{"id":33777,"date":"2019-12-19T22:30:44","date_gmt":"2019-12-20T03:30:44","guid":{"rendered":"https:\/\/www.thenatureofcities.com\/?p=33777"},"modified":"2019-12-19T22:35:00","modified_gmt":"2019-12-20T03:35:00","slug":"tree-planting-in-green-urban-infrastructure","status":"publish","type":"post","link":"https:\/\/www.thenatureofcities.com\/TNOC\/2019\/12\/19\/tree-planting-in-green-urban-infrastructure\/","title":{"rendered":"Tree Planting in Green Urban Infrastructure"},"content":{"rendered":"<p><a href=\"#Spanish\">Lea esto en espa\u00f1ol.<\/a><\/p>\n<figure class=\"wp-block-pullquote\"><blockquote>We need a rethink of the way cities are planned and built. That is why ecology, biology, and climatology are disciplines that have acquired a greater relevance in landscaping and the planning and design of urban open spaces.<\/blockquote><\/figure>The functions of today&#8217;s green are defined mainly by the needs that were conceived in the hygienist movement linked to the industrial city of the nineteenth century. Environmental pollution was the driving force behind public open spaces at that time, and at that time, the need for socialization and recreation was recognized. Today&#8217;s green space is heir to the industrial city, and although the need for clean air and social interaction continues, the environmental challenges facing cities in the 21st century involve reformulating the concept of green space.<\/p>\n<p>Today&#8217;s urban green needs to be understood as an ecological infrastructure, which acts as a structuring element of the ecological functions needed in the city. It is fundamental in the reproduction of so many natural processes in the city: constituting corridors of connection with the natural habitats of the environment, increasing the degree of biological diversity and the auto-generative capacity of the ecosystem itself, as well as an important role in the prevention of the &#8220;heat island&#8221; effect, the resilience of cities to climate change, among others.<\/p>\n<p>The functionality of green, in terms of urban infrastructure, refers to the possibility of assuming the urban green system as an instrument to attenuate and guide the urban development of the city, giving it a connotation of high environmental quality, in which the green infrastructure forms the structure. The reality is that the systemic approach of the territory must be translated into a systemic approach of the city, which forms part of the territory, in such a way that the city must be reconnected to the territorial biophysical matrix. That is why green spaces play a central role: to respond to ecological and environmental problems.<\/p>\n<p>Another of the ideal conceptions of current green spaces is that they are intended to constitute a system, that is to say, that they are conceived as a communicated and continuous whole, where the set of the different pieces has more value than the simple sum.<\/p>\n<p>The continuity of the green system is opposed to ghettoization. The city must incorporate green areas as part of its own fabric, and not as a good to be sought far from it. When configured in the urban fabric in the form of a complex network and related to the system of peri-urban open spaces, it represents an effective solution for the improvement of the urban ecosystem. In this sense, the urban green network assumes the connotations of a true and own infrastructure that, along with the others, assumes structural functions of the organization of the city.<\/p>\n<p>Thus, the new green systems are built from the idea of recovering lost ecological connectivities, but also on the basis of each of the new spaces that can be established. A concept that goes hand in hand with an integral vision of the landscape, whether natural or human-made. This integral vision allows a better protection of the landscape through the introduction of corridors that link the urban space with the rural and forest. This initiative is evident in the planning of cities such as Amsterdam, Munich and Berlin.<\/p>\n<p><strong>Urban ecology and green infrastructure<\/strong><\/p>\n<p>Urban ecology proposes a different way of understanding the city, as an ecosystem. The idea of analyzing the city as a living system is nothing new, there is no notion of this concept since Patrick Geddes, considered the father of urban ecology, in 1904 with his &#8220;City developments&#8221;. But it was not until 1973 that the importance of urban ecosystem analysis was seriously recognized in UNESCO&#8217;s Man and Biosphere program.<\/p>\n<p>To better understand the concept, reference is made first of all to the natural ecosystem, which is nothing more than a set of biotic and abiotic elements that interrelate with each other, producing flows of matter and energy between them. Biotic elements (living beings) need to degrade energy and materials to stay alive, but in natural ecosystems it is only plants that have the possibility of regenerating this energy through photosynthesis.<\/p>\n<p>The following is a brief summary of the characteristics of the city that are derived from urban ecology:<\/p>\n<ul>\n<li>Cities do not produce any of the resources they consume and need to exploit other ecosystems in order to function. This is why, from the point of view of ecological productivity, the urban ecosystem is considered a heterotropic system (Naredo and Rueda, 1998), which feeds on others, depending on other natural and agricultural ecosystems that are often found at great distances from the city.<\/li>\n<li>In the city, most of the flow of resources that it imports to function\u2014matter, energy and information\u2014is done horizontally (through transport systems such as railways, highways, energy networks), unlike natural ecosystems that do so, in most cases, vertically. In other words, the metabolism of cities is linear (Rueda, 1999). Dependent on fossil fuel and emitter of greenhouse gases<\/li>\n<li>The resources (matter, water and energy) once consumed and metabolized in the city, are returned to the ecological system in the form of solid (waste), liquid (wastewater), and gaseous (air pollution) pollution.<\/li>\n<li>In urban areas the &#8220;natural&#8221; conditions of a territory are transformed, from the soil and subsoil, altering the water permeability, the reduction of the vegetal layer, the climate etc. Giving rise to altered natural processes, which therefore will no longer be altered, becoming ecological processes proper to the urban system.<\/li>\n<\/ul>\n<p>The alteration caused by cities on natural ecosystems can be felt through micro-climatic modifications and imbalances in natural cycles, mainly carbon dioxide (CO<sub>2<\/sub>), nitrogen (N), carbon monoxide (CO), sulphur dioxide (SO<sub>2<\/sub>), ozone (O<sub>3<\/sub>), the natural water cycle. These alterations caused by the city are collected by the following areas of environmental action:<\/p>\n<p><u>Atmosphere<\/u>. The atmospheric affectation is characterized mainly by the increase of the environmental pollution, pollution, especially increase of the emissions of CO<sub>2<\/sub> and CO, linked to the consumption of fossil fuels. This is closely related to the model of a city dependent on transport networks to obtain the resources it needs and to function internally. At the same time, nitrogen dioxide (NO<sub>2<\/sub>), produced by combustion in motor vehicles and power plants, when reacting with volatile organic compounds, such as hydrocarbon gases, in the presence of abundant sunlight, generates tropospheric ozone (O<sub>3<\/sub>), which is why there will be higher ozone concentrations when solar radiation is more intense, in the case of Panama, this would occur mainly during the dry season. It should be noted that ozone causes health problems ranging from eye irritations, nostrils, bronchial tubes and lung infections.<\/p>\n<p><u>Water cycle<\/u>. Cities affect the water cycle through the extraction of water in natural spaces, and water pollution, causing alteration of natural aquifers, and generating floods in the urban environment, due to the lack of vegetation cover in the city, increasing surface runoffs.<\/p>\n<p><u>Energy<\/u>. The high consumption of energy in the city contributes to the exhaustion of non-renewable energies, which in turn increases greenhouse gas emissions, contributing to climate change. At the same time, the phenomenon (heat island effect), generated by urban models of the high density of constructions and heat accumulating materials (concrete, asphalt, etc.), raises the urban temperature.<\/p>\n<p>Finally, energy combustion also releases other substances that contribute to air pollution by deteriorating air quality.<\/p>\n<p><u>Biodiversity<\/u>. The urbanized space has usually led to the loss of a natural land cover, in not a few cases this translates into loss of habitat for fauna and flora. In addition, cities represent an interruption of the territory&#8217;s ecological connections, making it difficult in both cases to conserve biodiversity.<\/p>\n<p>Cities form complex systems in which numerous relationships and exchanges of matter and energy take place, but at the same time they are the main exploiters of natural ecosystems and their connections extend over the entire planet, being responsible for global entropic growth. In such a way that the cities have become parasites of the environment, consuming resources and at the same time contaminating the ecological systems that in turn deteriorate the habitability of the city itself. In this scenario, it is evident the need for structural changes in urban spaces, in different areas. One of them is the reconversion of urban vegetation in such a way that it responds, not to all of them, but to several of the urban environmental problems and future challenges.<\/p>\n<p><strong>The role of tree planting in the construction of green urban infrastructure<\/strong><\/p>\n<p>How can vegetation and green spaces respond to the ecological and environmental problems of the city, and provide solutions to achieve an environmentally balanced urban planning?\u00a0 The new approaches to nature in the city are no longer limited to a pleasant space and ornamental vegetation, now are priority objectives ranging from the habitability of open spaces for the population, the importance of spatial continuity within the city, habitat for biodiversity and climate change.<\/p>\n<p><span style=\"text-decoration: underline;\">Water cycle<\/span><\/p>\n<p>The water cycle when entering the urban system suffers a series of alterations that translate into environmental impacts and hydrological risks, which can be prevented or mitigated with various tree planting strategies. On the one hand, excessive urban water consumption prevents the long-term protection of water resources and, on the other hand, the rainfall regime is changing due to climate change. Extreme events alternate, droughts and high intensity torrential rains are expected to become more frequent, as global temperatures continue to rise. As a result, the risk of droughts and floods increases.<\/p>\n<p>This translates into the promotion of sustainable water consumption, which in terms of green infrastructure implies the use of vegetation adapted to the climate, so that during the dry season irrigation is not required. At the same time, rainwater in an impermeable environment such as an urban one conflicts with the water network that naturally crosses urban areas, which as a whole represents a risk of flooding. Therefore, an urban policy of green infrastructure must be aimed at the recovery of the banks of urban rivers, mainly with the planting of riverside tree vegetation, and also the increase of the vegetated surface within the urban fabric. The creation of urban forests is essential to control erosion and protect the water network of cities.<\/p>\n<p>Every year, floods cause considerable damage in urban areas.<\/p>\n<p>Green infrastructure can contribute to rainwater management, absorbing water in a greater percentage of vegetated surface, through controlled and designed temporary flooding systems of squares (United States Environmental Protection Agency, 2016), or systems of bio-retention of rainwater, turning these into fundamental equipment in the design of squares, urban and periurban parks, and even in green cords of public roads. At the same time, tree-planting not only helps to absorb rainwater, but also controls runoff at source, reducing erosion and pollution in water courses (Vargas et al 2008).<\/p>\n<figure id=\"attachment_33779\" aria-describedby=\"caption-attachment-33779\" style=\"width: 604px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/www.thenatureofcities.com\/2019\/12\/19\/tree-planting-in-green-urban-infrastructure\/dsc09507\/\" rel=\"attachment wp-att-33779\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-33779 size-large\" src=\"https:\/\/www.thenatureofcities.com\/TNOC\/wp-content\/uploads\/2019\/12\/DSC09507-747x560.jpg\" alt=\"\" width=\"604\" height=\"453\" srcset=\"https:\/\/www.thenatureofcities.com\/TNOC\/wp-content\/uploads\/2019\/12\/DSC09507-747x560.jpg 747w, https:\/\/www.thenatureofcities.com\/TNOC\/wp-content\/uploads\/2019\/12\/DSC09507-1536x1152.jpg 1536w, https:\/\/www.thenatureofcities.com\/TNOC\/wp-content\/uploads\/2019\/12\/DSC09507-100x75.jpg 100w, https:\/\/www.thenatureofcities.com\/TNOC\/wp-content\/uploads\/2019\/12\/DSC09507.jpg 2048w\" sizes=\"auto, (max-width: 604px) 100vw, 604px\" \/><\/a><figcaption id=\"caption-attachment-33779\" class=\"wp-caption-text\">The conservation of gallery forests and the maintenance of banks of rivers free of construction are fundamental strategies in the constitution of a green infrastructure that prevents floods. Photo: Graciela Arosemena. Former Clayton Fort, Ex-Canal Zone (Panama).<\/figcaption><\/figure>\n<p><strong>Implications for improving air quality<\/strong><\/p>\n<p>City trees can reduce some air pollutants. Pollution is reduced directly when dust and smoke particles are trapped in vegetation. In addition, plants absorb toxic gases, especially those caused by the combustion of motor vehicles.<\/p>\n<p>At the same time, high temperatures accelerate the formation of pollution, such as tropospheric ozone (O<sub>3<\/sub>). In this sense, the moderating effect of vegetation, especially trees, can reduce temperatures and in turn reduce the formation of pollutants. Recently, the U.S. Environmental Protection Agency (EPA) recognized that arborization is a measure to reduce O<sub>3<\/sub>.<\/p>\n<p>Carbon dioxide is another air pollutant that contributes to climate change. Urban arborization can reduce CO<sub>2<\/sub> levels by capturing the gas through its leaves with photosynthesis, and sequestering CO<sub>2<\/sub> in the trunk, branches and roots while it is growing; in addition, regulation of the urban microclimate reduces extreme temperatures and reduces the energy consumption associated with air conditioners. (Sorensen, Barzetti, Keipi, &amp; Williams, 1998).<\/p>\n<p>Trees extract pollutants in two main ways:<\/p>\n<ul>\n<li>They incorporate gases and pollutants through the stomata of their leaves. The gases enter the interior of the leaves, where there is a lot of water. Many gases dissolve and change state.<\/li>\n<li>They capture particles on the surface of the leaves.<\/li>\n<li>Ideally, the tree should have many leaves and be large in size.<\/li>\n<li>They absorb polluting gases (e.g. NO2, SO2), intercept PM10 (dust, ash, dust and smoke).<\/li>\n<\/ul>\n<p>In a study of urban forests in Honolulu (Hawaii), it found that 43,817 trees in the city remove about 9 tons of air pollutants, an environmental service estimated at $47, 365.00 dollars (Vargas, McPherson, Peper, &amp; Et. al., 2007).<\/p>\n<p>Thus, when choosing tree species to be located in urban open spaces, consideration should be given to the morphological characteristics that are most suitable for the functions of absorption of polluting gases, or for the prevention of ozone formation. Ornamental aspects are thus left in the background.<\/p>\n<figure id=\"attachment_33781\" aria-describedby=\"caption-attachment-33781\" style=\"width: 1536px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/www.thenatureofcities.com\/2019\/12\/19\/tree-planting-in-green-urban-infrastructure\/dsc09540\/\" rel=\"attachment wp-att-33781\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-33781 size-full\" src=\"https:\/\/www.thenatureofcities.com\/TNOC\/wp-content\/uploads\/2019\/12\/DSC09540.jpg\" alt=\"\" width=\"1536\" height=\"2048\" \/><\/a><figcaption id=\"caption-attachment-33781\" class=\"wp-caption-text\">Road trees are essential to keep the passage of automobiles shaded and to prevent pollutants such as NO and non-metallic hydrocarbons from mobile sources (automobiles) from becoming ozone due to the action of solar radiation. Photo: Graciela Arosemena<\/figcaption><\/figure>\n<p><strong>Climate regulation and resilience to climate change<\/strong><\/p>\n<p>One of the main issues facing urban societies in the 21st century is how to curb their greenhouse gas emissions and adapt to the already present effects of climate change. In Panama, for example, one of the effects associated with climate change is the increase in absolute temperature, which could increase by between 1 and 3\u00baC during the months with the highest temperatures: April and May (CATHALAC, 2008). And absolute maximum temperature events above 38\u00baC would be exceeded by 2020. (CATHALAC, 2008).<\/p>\n<p>In cities with hot climates, extreme temperature episodes are expected to be more severe due to adverse baseline conditions associated with the &#8216;urban heat island&#8217; effect (UN-HABITAT, 2011). A problem generated by the high density of constructions and heat accumulating materials (concrete, asphalt, etc.), by the concentration of anthropogenic heat generating activities (traffic, air conditioning, etc.). In fact, according to the climate change vulnerability maps of the different ecological units in Panama, in terms of temperature, the Pacific Metropolitan Area (Panama) has a high average vulnerability to changes in temperature increase (Tremblay &amp; Ross, 2007).<\/p>\n<p>Bearing in mind that the temperature increase of 1\u00baC implies an increase in energy consumption in air conditioning of between 3 and 4%, and can reach up to 10%, energy consumption could increase up to 30% with an increase in temperature of 3\u00baC.<\/p>\n<p>In order to mitigate the effects of the heat island and reduce high energy consumption it is essential to plan the woodland as a natural climate for the urban microclimate.<\/p>\n<p>Key environmental variables for human thermal comfort include solar radiation, urban surface temperature, air temperature, humidity and wind speed. Research has shown that urban tree planting can improve these environmental variables through the prevention of solar radiation and the reduction of heating of building surfaces, combined with the effect of reducing air temperature through evapotranspiration. (Akbari &amp; et al., 1992) (Simpson &amp; McPherson, 1996); (Georgi &amp; Zafiriadis, 2006). In short, urban woodland intervenes in the modification of the climate in warm zones, mainly in the following three effects (Akbari H., 2002):<\/p>\n<p><u>Shading<\/u>: The treetops intercept solar radiation, preventing the heating of buildings, asphalt and pavements.<\/p>\n<p>Evapotranspiration: The transpiration of the leaves requires heat energy captured from the environment, producing a decrease in the temperature in the environment.<\/p>\n<figure id=\"attachment_33780\" aria-describedby=\"caption-attachment-33780\" style=\"width: 604px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/www.thenatureofcities.com\/2019\/12\/19\/tree-planting-in-green-urban-infrastructure\/dsc09510\/\" rel=\"attachment wp-att-33780\"><img loading=\"lazy\" decoding=\"async\" class=\"size-large wp-image-33780\" src=\"https:\/\/www.thenatureofcities.com\/TNOC\/wp-content\/uploads\/2019\/12\/DSC09510-747x560.jpg\" alt=\"\" width=\"604\" height=\"453\" \/><\/a><figcaption id=\"caption-attachment-33780\" class=\"wp-caption-text\">The treetops generate a protective screen against solar radiation, minimising the heat island effect in cities. Photo: Graciela Arosemena.<\/figcaption><\/figure>\n<p>The capacity of trees to modify the urban climate, above all to reduce high temperatures, depends fundamentally on the degree of tree cover, i.e. the percentage of urban surface located under the projection of the tree tops, as well as the type and density of the tops. On the refreshing effect of vegetation in urban environments, it has been reported that measurements made in different cities of the North, such as the study carried out in the Berlin Zoo (Hoerbert, 1982). In this study the temperature differences were 5-7\u00b0C and the relative humidity varied 10% and reported variations between 3 and 8 \u00baC for different compositions and species of trees, the measurements were also made at different times of the year.<\/p>\n<p>Measurements on the effect of shadows have been made in studies where design, building typologies, landscape and climates were assessed, they found that energy savings would be around 25% to 80%. The greatest savings were associated with the density and extent of shadows, solar radiation being the largest source of heat gain (Simpson &amp; McPherson, 1996).<\/p>\n<p><strong>Conservation of biodiversity and natural heritage<\/strong><\/p>\n<p>From an environmental point of view, urban open spaces, in addition to exercising functions of climate control or filtering atmospheric pollution, among others, must guarantee the conservation of biological diversity and a permeability that allows ecological connections, maintaining environmental and landscape values.<\/p>\n<p>Cities can play a fundamental role in the conservation of biodiversity through strategies that include the introduction of ecosystems and habitats into the urban fabric, or the preservation of pre-existing ones, as well as the creation of continuous urban green spaces that guarantee biological connectivity and control territorial fragmentation (Generalitat de Catalunya, 2003). A fundamental objective of this is to establish as the backbone of the territory a continuous network of natural spaces that crosses the city and connects peri-urban natural spaces with urban natural spaces.<\/p>\n<p>The need to increase the nature of the city and strengthen the connections between the city and its surroundings is evident, and one of the key pieces for achieving this are the urban tree planting strategies, aimed at effectively providing habitat for species of birds, mainly mammals. Trees provide habitat, shelter and food for local fauna. In order to guarantee an arborization that restores the ecological biodiversity in the cities, it is necessary to choose native plant species, which are the ones to which the fauna is accustomed. In fact, the use of exotic species is one of the direct causes of threat to biodiversity and ecosystem conservation, along with habitat destruction (Aguirre Mu\u00f1oz &amp; Mendoza Alfaro).<\/p>\n<p>On the contrary, native tree species in urban environments provide food for fauna, which would be reduced or absent in the case of exotic trees. In addition, native trees increase the richness and diversity of fauna, so an important strategy of urban arborization is the recognition which native species of trees are habitat of certain fauna, in order to establish a biodiverse habitat in the urban environment.<\/p>\n<figure id=\"attachment_33782\" aria-describedby=\"caption-attachment-33782\" style=\"width: 604px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/www.thenatureofcities.com\/2019\/12\/19\/tree-planting-in-green-urban-infrastructure\/img_3239-2\/\" rel=\"attachment wp-att-33782\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-33782 size-large\" src=\"https:\/\/www.thenatureofcities.com\/TNOC\/wp-content\/uploads\/2019\/12\/IMG_3239-2-747x560.jpg\" alt=\"\" width=\"604\" height=\"453\" \/><\/a><figcaption id=\"caption-attachment-33782\" class=\"wp-caption-text\">Metropolitan Natural Park, in the middle of Panama City. Humid forest to dry tropical biodiversity reserve that provides environmental services such as sponge rainwater and sink of pollutant gases. For all these functions, it should be considered a green infrastructure facility of the city. Photo: Graciela Arosemena.<\/figcaption><\/figure>\n<p><strong>A new model of urban open spaces<\/strong><\/p>\n<p>The impact that local and global environmental problems are having on urban environments is unprecedented in urban history, and this calls not only for a rethink of the way cities are planned and built, but also for a new approach to the system of free and green urban spaces. That is why ecology, biology, and climatology are disciplines that have acquired a greater relevance in landscaping and the planning and design of urban open spaces.<\/p>\n<p>No city can meet the environmental challenges of the 21st century without considering the construction of ecological green infrastructure.<\/p>\n<p><strong>Graciela Arosemena D\u00edaz<\/strong><br \/>\nPanama City<\/p>\n<p>On <a href=\"https:\/\/www.thenatureofcities.com\" target=\"_blank\" rel=\"noopener noreferrer\">The Nature of Cities<\/a><\/p>\n<p>&nbsp;<\/p>\n<p><strong>References<\/strong><\/p>\n<p>Akbari, &amp; et al. (1992). <em>Cooling our communities: A Guidebook to tree planting and light colored surfacing. .<\/em>U.S.A EPA, Ofice of Policy Anallysis, Climate Change Division, Washington, D.C.<\/p>\n<p>CATHALAC. (2008). <em>Potential Impacts of Climate Change and Biodiversity in Central America, Mexico and Dominican Republic.<\/em><\/p>\n<p>Georgi, N., &amp; Zafiriadis, K. (2006). The Impact of trees on microclimate in urban areas. <em>Urban Ecosyst<\/em> .<\/p>\n<p>Hoerbert, M. (1982). A climatic and air hygienic aspects in planning of iner-city open spaces: Berliner Grosser Tiergartes. <em>Energy and Buildings<\/em> <em>, 5<\/em> (1).<\/p>\n<p>Naredo, J. (1997). Sobre el origen, eluso y el contenido del t\u00e9rmino sostenible. <em>Cuadernos de Guincho<\/em> .<\/p>\n<p>ONU-HABITAT. (2011). <em>Informe mundial sobre asentamientos humanos. Las ciudades y el cambio clim\u00e1tico: Orientaci\u00f3n para pol\u00edtcas.<\/em> Londres: Earthscan.<\/p>\n<p>Rueda, S (1995)\u00a0 Ecologia Urbana: Barcelona i la seva Regi\u00f3 Metropolitana com a referents. Ed. Beta Editoria<\/p>\n<p>Simpson, J., &amp; McPherson, E. (1996). Potential of tree shade for reducing residential energy use in California. <em>Journal of Arboriculture<\/em> (22).<\/p>\n<p>Sorensen, M., Barzetti, V., Keipi, K., &amp; Williams, J. (1998). <em>Manejo de las \u00e1reas verdes urbanas. Documento de buenas pr\u00e1cticas.<\/em> Banco Interamericano de Desarrollo. Divisi\u00f3n de Medio Ambiente del Departamento de Desarrollo Sostenible., Washington, D.C.<br \/>\n<a name=\"Spanish\"><\/a><\/p>\n<h2 style=\"text-align: center;\"><strong>* * *<\/strong><\/h2>\n<h2>La arborizaci\u00f3n en la infraestructura verde urbana<\/h2>\n<figure class=\"wp-block-pullquote\"><blockquote>El impacto que est\u00e1n generando los problemas ambientales, locales y globales, sobre los entornos urbanos no tienen precedentes en la historia urbana. Es fundamental un nuevo planteamiento del sistema de espacios libres y verdes urbano. Es por ello que la ecolog\u00eda, biolog\u00eda y la climatolog\u00eda, son disciplinas que han adquirido una mayor relevencia en el paisajismo, en la planificaci\u00f3n y dise\u00f1o de espacios abiertos.<\/blockquote><\/figure>Las funciones del verde actual est\u00e1n definidas principalmente por las necesidades que fueron concebidas\u00a0 en el movimiento higienista vinculado a la ciudad industrial del siglo XIX. La contaminaci\u00f3n ambiental fue el impulsor de los espacios abiertos p\u00fablicos en aquel momento, y paralelamente, fue reconocida la necesidad de socializaci\u00f3n y recreaci\u00f3n. El espacio verde actual es heredero de la ciudad industrial, y aunque la necesidad de aire limpio e interacci\u00f3n social contin\u00faan vigentes, los retos ambientales \u2013 a los que se enfrentan las ciudades en el siglo XXI, implican reformular el concepto de espacio verde.<\/p>\n<p>El verde urbano en la actualidad requiere ser entendido como una infraestructura ecol\u00f3gica, que act\u00faa como elemento vertebrador de las funciones ecol\u00f3gicas necesarias en la ciudad. Es\u00a0 fundamental en la reproducci\u00f3n de tantos \u00a0procesos naturales en la ciudad: constituyendo corredores de conexi\u00f3n con los h\u00e0bitats naturales del entorno, incrementando el grado de diversidad biol\u00f3gica y la capacidad auto generativa del ecosistema mismo, as\u00ed como un importante papel en la prevenci\u00f3n del efecto \u201cisla de calor\u201d, la resiliencia de las ciudades al cambio clim\u00e1tico, entre otros.<\/p>\n<p>La funcionalidad del verde, en t\u00e9rminos de infraestructura urbana, se refiere a la posibilidad de asumir el sistema verde urbano como instrumento para atenuar y orientar el desarrollo urban\u00edstico de la ciudad, imprimiendo a este una connotaci\u00f3n de elevada calidad ambiental, en la cual la infraestructura verde conforma la estructura.<\/p>\n<p>La realidad es que la aproximaci\u00f3n sist\u00e9mica del territorio se debe traducir en una aproximaci\u00f3n sist\u00e9mica de la ciudad, que forma parte del territorio, de tal forma que la ciudad debe ser reconectada a la matriz biof\u00edsica territorial. Por eso los espacios verdes, desempe\u00f1an un papel capital: responder a los problemas ecol\u00f3gicos y ambientales.<\/p>\n<p>Otra de las concepciones ideales de los espacios verdes actuales es que se pretende que constituyan un sistema, esto es, que se conciban como un todo comunicado y continuo, donde el conjunto de las distintas piezas tenga m\u00e1s valor que la simple suma.<\/p>\n<p>La continuidad del sistema verde se opone a la guetizaci\u00f3n. La ciudad debe incorporar las \u00e1reas verdes como parte de su propio tejido, y no como un bien que hay que buscar lejos de \u00e9l. Cuando se configura en el tejido urbano en forma de red compleja y se relaciona al sistema de los espacios abiertos periurbanos, representa una soluci\u00f3n eficaz para el mejoramiento del ecosistema urbano.<\/p>\n<p>En este sentido, la red verde urbana asume las connotaciones de una verdadera y propia infraestructura que, a la par de las otras, asume funciones estructurales de la organizaci\u00f3n de la ciudad.<\/p>\n<p>As\u00ed, los nuevos sistemas verdes se construyen desde la idea de recuperar las conectividades ecol\u00f3gicas perdidas, pero tambi\u00e9n sobre la base de cada uno de los nuevos espacios que se pueden establecer. Concepto que va de la mano de la visi\u00f3n integral del paisaje, ya sea natural o antropizado. Esta visi\u00f3n integral permite una mejor protecci\u00f3n del paisaje a trav\u00e9s de la introducci\u00f3n de corredores que vinculen el espacio urbano con el rural y forestal. Esta iniciativa se hace evidente en la planificaci\u00f3n de ciudades como \u00c1msterdam, M\u00fanich y Berl\u00edn.<\/p>\n<p><strong>Ecolog\u00eda urbana e infraestructura verde<\/strong><\/p>\n<p>La ecolog\u00eda urbana plantea una forma distinta de comprender la ciudad, como un ecosistema. No es nada nueva la idea de analizar la ciudad como un sistema vivo, se tiene noci\u00f3n de este concepto desde Patrick Geddes, considerado el padre de la ecolog\u00eda urbana, en 1904 con su \u201cCity developments\u201d. Pero no fue hasta el a\u00f1o 1973 cuando fue reconocida seriamente la importancia del an\u00e1lisis del ecosistema urbano en el programa Man and Biosphere de la UNESCO.<\/p>\n<p>Para comprender mejor el concepto, se hace referencia primeramente al ecosistema natural, el cual no es m\u00e1s que un conjunto de elementos bi\u00f3ticos y abi\u00f3ticos que interrelacionan entre s\u00ed, produci\u00e9ndose entre ellos flujos de materia y energ\u00eda. Los elementos bi\u00f3ticos (los seres vivos), necesitan degradar energ\u00eda y materiales para mantenerse vivos, pero en los ecosistemas naturales son \u00fanicamente las plantas quienes tienen la posibilidad de regenerar esta energ\u00eda, a trav\u00e9s de la fotos\u00edntesis.<\/p>\n<p>A continuaci\u00f3n, se resumen brevemente cu\u00e1les son las caracter\u00edsticas de la ciudad que se desprenden de la ecolog\u00eda urbana:<\/p>\n<p>Las ciudades no producen ninguno de los recursos que consumen y necesitan explotar otros ecosistemas para poder funcionar. Es por ello que, desde el punto de vista de la productividad ecol\u00f3gica, el ecosistema urbano es considerado un sistema heter\u00f3trofo (Naredo, 1997; Rueda, 1995), &#8211; que se alimenta de otros -, al depender de otros ecosistemas naturales y agr\u00edcolas que muchas veces se encuentran a grandes distancias de la ciudad.<\/p>\n<ul>\n<li>En la ciudad, la mayor parte del flujo de los recursos que importa para funcionar &#8211; materia, energ\u00eda e informaci\u00f3n -, se realiza en sentido horizontal (a trav\u00e9s de sistemas de transportes como el ferrocarril, autov\u00edas, redes de energ\u00eda), a diferencia de los ecosistemas naturales que lo hacen, en la mayor\u00eda de los casos, de forma vertical. En otras palabras, el metabolismo de las ciudades es lineal (Rueda, 1999). Dependiente de combustible f\u00f3sil y emisor de gases efecto invernadero<\/li>\n<li>Los recursos (materia, agua y energ\u00eda) una vez consumidos y metabolizados en la ciudad, son devueltos al sistema ecol\u00f3gico en forma de contaminaci\u00f3n s\u00f3lida (residuos), l\u00edquida (aguas residuales), y gaseosa (contaminaci\u00f3n atmosf\u00e9rica).<\/li>\n<li>En las zonas urbanas las condiciones \u201cnaturales\u201d de un territorio son transformadas, desde el suelo y el subsuelo, alterando la permeabilidad h\u00eddrica, la reducci\u00f3n de la capa vegetal, el clima etc. Dando lugar a procesos naturales alterados, que por tanto ya no lo ser\u00e1n m\u00e1s, pasando a ser procesos ecol\u00f3gicos propios del sistema urbano.<\/li>\n<\/ul>\n<p>La alteraci\u00f3n provocada por las ciudades sobre los ecosistemas naturales se pueden palpar a trav\u00e9s modificaciones micro clim\u00e1ticas y de los desequilibrios en los ciclos naturales, principalmente del di\u00f3xido de carbono (CO<sub>2 <\/sub>), del nitr\u00f3geno (N),\u00a0 mon\u00f3xido de carbono (CO), di\u00f3xido de azufre (SO<sub>2<\/sub>), ozono (O<sub>3<\/sub>), el ciclo natural del agua.\u00a0 Estas alteraciones ocasionadas por la ciudad son recogidas por los siguientes \u00e1mbitos de acci\u00f3n ambiental:<\/p>\n<p><strong>Atm\u00f3sfera.<\/strong> La afectaci\u00f3n atmosf\u00e9rica se caracteriza principalmente por el aumento de la contaminaci\u00f3n ambiental, poluci\u00f3n, especialmente aumento de las emisiones de CO<sub>2<\/sub> y CO, vinculados al consumo de combustibles f\u00f3siles. Esto est\u00e1 estrechamente relacionado con el modelo de ciudad dependiente de redes de transportes para obtener los recursos que necesita y para funcionar internamente. Paralelamente, el di\u00f3xido de nitr\u00f3geno (NO<sub>2<\/sub>), producido por la combusti\u00f3n en veh\u00edculos motorizados y plantas el\u00e9ctricas, al reaccionar con compuestos org\u00e1nicos vol\u00e1tiles, como gases hidrocarburos, en presencia de abundante luz solar, genera ozono troposf\u00e9rico (O<sub>3<\/sub>), es por esto que habr\u00e1 mayores concentraciones de ozono cuando la radiaci\u00f3n solar es m\u00e1s intensa, en el caso de Panam\u00e1, esto ocurrir\u00eda principalmente durante la estaci\u00f3n seca. Cabe se\u00f1alar que el ozono provoca problemas para la salud desde irritaciones en los ojos, fosas nasales, hasta bronquios e infecciones pulmonares.<\/p>\n<p><strong>Ciclo h\u00eddrico<\/strong>. Las ciudades inciden sobre el ciclo del agua a trav\u00e9s de la extracci\u00f3n de agua en espacios naturales, y la contaminaci\u00f3n de las aguas, provocando alteraci\u00f3n de acu\u00edferos naturales, y generando en el medio urbanizado inundaciones, debido la falta de cobertura vegetal en la ciudad, aumentando escorrent\u00edas superficiales.<\/p>\n<p><strong>\u00c1mbito energ\u00e9tico.<\/strong> El alto consumo de energ\u00eda en la ciudad contribuye al agotamiento de energ\u00edas no renovables, que a su vez aumenta emisiones de gases efecto invernadero, contribuyendo al cambio clim\u00e1tico.<\/p>\n<p>Paralelamente el fen\u00f3meno (<em>efecto de \u2018isla de calor\u2019<\/em>), generado por modelos urbanos de la alta densidad de construcciones y materiales acumuladores de calor (hormig\u00f3n, asfalto, etc.), eleva la temperatura urbana.<\/p>\n<p>Por \u00faltimo, la combusti\u00f3n energ\u00e9tica adem\u00e1s libera otras sustancias que contribuyen a la contaminaci\u00f3n atmosf\u00e9rica deteriorando la calidad del aire.<\/p>\n<p><strong>Biodiversidad.\u00a0 <\/strong>El espacio urbanizado, usualmente ha conllevado la p\u00e9rdida de una cobertura de suelo natural, en no pocos casos ello se traduce en p\u00e9rdida de h\u00e1bitat de fauna y flora. Adem\u00e1s, las ciudades representan una interrupci\u00f3n de las conexiones ecol\u00f3gicas del territorio, dificultando en ambos casos la conservaci\u00f3n de la biodiversidad.<\/p>\n<p>Las ciudades forman sistemas complejos en las cuales se producen numerosas relaciones e intercambios de materia y energ\u00eda, pero a su vez son las principales explotadoras de los ecosistemas naturales y sus conexiones se extienden sobre todo el planeta, siendo responsables del crecimiento entr\u00f3pico global.<\/p>\n<p>De tal forma que las ciudades se han convertido en par\u00e1sitos del entorno, consumiendo recursos y a su vez contaminando los sistemas ecol\u00f3gicos que a su vez deterioran la habitabilidad de la propia ciudad. En este escenario, es evidente la necesidad de cambios estructurales de los espacios urbanos, en diversos \u00e1mbitos. Uno de ellos es la reconversi\u00f3n de la vegetaci\u00f3n urbana de forma tal que responda, no a todos, pero a varios de los problemas ambientales urbanos y los retos futuros.<\/p>\n<p><strong>El papel de la arborizaci\u00f3n e<\/strong><strong>n la construcci\u00f3n de la infraestructura verde urbana<\/strong><\/p>\n<p>\u00bfC\u00f3mo la vegetaci\u00f3n y los espacios verdes puede responder a los problemas ecol\u00f3gicos y ambientales de la ciudad, y dar soluciones para conseguir un planeamiento urbano ambientalmente equilibrado&#8217;.\u00a0 Los nuevos planteamientos de la naturaleza en la ciudad ya no se limitan a un espacioagradable y con vegetaci\u00f3n ornamental, ahora son prioritarios objetivos que van desde<\/p>\n<p>la habitabilidad de los espacios libres para la poblaci\u00f3n, la importancia de la continuidad espacial dentro de la ciudad, h\u00e1bitat para la biodiversidad y el cambio clim\u00e1tico.<\/p>\n<p><strong>Ciclo del agua<\/strong><\/p>\n<p>El ciclo del agua al entrar en el sistema urbano sufre una serie de alteraciones que se traducen en impactos ambientales y en riesgos hidrol\u00f3gicos, que pueden ser prevenidos o mitigados con diversas estrategias de arborizaci\u00f3n. Por un lado, el consumo urbano desmedido de agua impide la protecci\u00f3n a largo t\u00e9rmino de los recursos h\u00eddricos y, por otro lado, el r\u00e9gimen de precipitaci\u00f3n pluvial se est\u00e1 modificando a causa del cambio clim\u00e1tico. Los eventos extremos se van alternando, sequ\u00edas y lluvias torrenciales de alta intensidad se espera que sean m\u00e1s frecuentes, toda vez que contin\u00faa aumentando la temperatura global. Como resultado, el riesgo de sequ\u00edas y de inundaciones se incrementa.<\/p>\n<p>Esto se traduce en la promoci\u00f3n del consumo sostenible de agua, lo que en t\u00e9rminos de la infraestructura verde implica el uso de vegetaci\u00f3n adaptada al clima, de tal forma que durante la estaci\u00f3n seca no sea requerido el riego. Paralelamente el agua lluvia en un ambiente impermeable como el urbano, entra en conflicto con la red h\u00eddrica que naturalmente atraviesa las zonas urbanas, lo que en su conjunto representa un riesgo de inundaci\u00f3n. Por lo que una pol\u00edtica urbana de infraestructura verde debe estar encaminada a la recuperaci\u00f3n de las riberas de los r\u00edos urbanos, principalmente con la siembra de vegetaci\u00f3n arb\u00f3rea de ribera, y adem\u00e1s el aumento de la superficie vegetada dentro del tejido urbano. La creaci\u00f3n de bosques urbanos es fundamental para controlar la erosi\u00f3n y proteger la red h\u00eddrica de las ciudades.<\/p>\n<p>Cada a\u00f1o, las inundaciones causan da\u00f1os considerables en las zonas urbanas.<\/p>\n<p>La infraestructura verde puede contribuir a gestionar el agua lluvia, absorbiendo agua en un mayor porcentaje de superficie vegetada, a trav\u00e9s de sistemas inundaci\u00f3n temporal controlada y dise\u00f1ada de plazas (United States Environmental Protection Agency, 2016), o sistemas de bio retenci\u00f3n de agua lluvia, convirti\u00e9ndose estos en un equipamiento fundamental en el dise\u00f1o de plazas, parques urbanos y periurbanos, e incluso en cordones verdes de las v\u00edas p\u00fablicas. Paralelamente, la arborizaci\u00f3n adem\u00e1s de contribuir a absorber el agua lluvia, controla la escorrent\u00eda en el origen, reduciendo erosi\u00f3n y contaminaci\u00f3n en los cursos de agua (Vargas, McPherson, J, Simpson, Peper, Gardner, &amp; Xiao, 2008).<\/p>\n<figure id=\"attachment_33779\" aria-describedby=\"caption-attachment-33779\" style=\"width: 604px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/www.thenatureofcities.com\/2019\/12\/19\/tree-planting-in-green-urban-infrastructure\/dsc09507\/\" rel=\"attachment wp-att-33779\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-33779 size-large\" src=\"https:\/\/www.thenatureofcities.com\/TNOC\/wp-content\/uploads\/2019\/12\/DSC09507-747x560.jpg\" alt=\"\" width=\"604\" height=\"453\" srcset=\"https:\/\/www.thenatureofcities.com\/TNOC\/wp-content\/uploads\/2019\/12\/DSC09507-747x560.jpg 747w, https:\/\/www.thenatureofcities.com\/TNOC\/wp-content\/uploads\/2019\/12\/DSC09507-1536x1152.jpg 1536w, https:\/\/www.thenatureofcities.com\/TNOC\/wp-content\/uploads\/2019\/12\/DSC09507-100x75.jpg 100w, https:\/\/www.thenatureofcities.com\/TNOC\/wp-content\/uploads\/2019\/12\/DSC09507.jpg 2048w\" sizes=\"auto, (max-width: 604px) 100vw, 604px\" \/><\/a><figcaption id=\"caption-attachment-33779\" class=\"wp-caption-text\">La conservaci\u00f3n de bosques de galer\u00eda y el mantenimiento de m\u00e1rgenes de los r\u00edos libres de edificaci\u00f3n, son estrategias fundamentales en la constituci\u00f3n de una infraestructura verde que prevenga inundaciones. Foto: Graciela Arosemena. Antiguo Fuerte Clayton, Ex-Zona del Canal (Panam\u00e1).<\/figcaption><\/figure>\n<p><strong>Implicaciones en la mejora de la calidad del aire<\/strong><\/p>\n<p>Los \u00e1rboles de la ciudad pueden reducir algunos contaminantes del aire. La contaminaci\u00f3n se reduce directamente cuando las part\u00edculas de polvo y humo quedan atrapadas en la vegetaci\u00f3n. Adem\u00e1s, las plantas absorben gases t\u00f3xicos, especialmente aquellos originados por la combusti\u00f3n de veh\u00edculos motorizados.<\/p>\n<p>Paralelamente, las altas temperaturas aceleran la formaci\u00f3n de contaminaci\u00f3n, como es el caso del ozono (O<sub>3<\/sub>) troposf\u00e9rico. En ese sentido el efecto moderador de la vegetaci\u00f3n, especialmente de la arborizaci\u00f3n puede reducir las temperaturas y a su vez reducir la formaci\u00f3n de contaminantes. Recientemente, la Agencia de Protecci\u00f3n Ambiental de Estados Unidos (EPA), reconoci\u00f3 que la arborizaci\u00f3n es una medida para reducir el O<sub>3.<\/sub><\/p>\n<p>El di\u00f3xido de carbono es otro de los compuestos contaminantes del aire que contribuye al cambio clim\u00e1tico. La arborizaci\u00f3n urbana puede reducir los niveles de CO<sub>2<\/sub> mediante la captaci\u00f3n del gas a trav\u00e9s de sus hojas con la fotos\u00edntesis, y el secuestro de CO<sub>2<\/sub> en tronco, ramas y ra\u00edces mientras est\u00e1 creciendo; y adem\u00e1s la regulaci\u00f3n del microclima urbano reduce las temperaturas extremas y se reduce el consumo energ\u00e9tico asociado a los aires acondicionados. (Sorensen, Barzetti, Keipi, &amp; Williams, 1998).<\/p>\n<p>Los \u00e1rboles extraen contaminantes de dos formas principalmente:<\/p>\n<ul>\n<li>Incorporan gases y contaminantes a trav\u00e9s de las estomas de sus hojas. Los gases ingresan al interior de las hojas, donde hay mucha agua. Muchos gases se disuelven y cambian de estado.<\/li>\n<li>Capturan part\u00edculas en la superficie de las hojas<\/li>\n<li>Lo ideal es que el \u00e1rbol tenga muchas hojas y sea de gran tama\u00f1o.<\/li>\n<li>Absorben gases contaminantes (por ejemplo, NO<sub>2<\/sub>, SO<sub>2<\/sub>), interceptan PM<sub>10<\/sub> (polvo, ceniza, polvo y humo)<sub>.<\/sub><\/li>\n<\/ul>\n<p><sub>\u00a0<\/sub>En un estudio sobre bosques urbanos en Honolulu (Hawaii), encontr\u00f3 que 43,817 \u00e1rboles en la ciudad remueven cerca de 9 toneladas de contaminantes atmosf\u00e9ricos, un servicio ambiental estimado en $47, 365.00 d\u00f3lares (Vargas, McPherson, Peper, &amp; Et. al., 2007).<\/p>\n<p>De forma tal que, en el momento de escoger las especies de \u00e1rboles para ser ubicados en los espacios abiertos urbanos, deben considerarse las caracter\u00edsticas morfol\u00f3gicas que sean m\u00e1s id\u00f3neas para las funciones de absorci\u00f3n de gases contaminantes, o para la prevenci\u00f3n de formaci\u00f3n de ozono. Los aspectos ornamentales quedan as\u00ed en un segundo plano.<\/p>\n<figure id=\"attachment_33781\" aria-describedby=\"caption-attachment-33781\" style=\"width: 604px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/www.thenatureofcities.com\/2019\/12\/19\/tree-planting-in-green-urban-infrastructure\/dsc09540\/\" rel=\"attachment wp-att-33781\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-33781\" src=\"https:\/\/www.thenatureofcities.com\/TNOC\/wp-content\/uploads\/2019\/12\/DSC09540-420x560.jpg\" alt=\"\" width=\"604\" height=\"805\" \/><\/a><figcaption id=\"caption-attachment-33781\" class=\"wp-caption-text\">El arbolado viario es fundamental para mantener sombreado el paso de los autom\u00f3viles y evitar que, por la acci\u00f3n de la radiaci\u00f3n solar, los contaminantes como NO, y los hidrocarburos no met\u00e1licos, provenientes de fuentes m\u00f3viles (autom\u00f3viles), se transformen en ozono. Foto: Graciela Arosemena<\/figcaption><\/figure>\n<p><strong>Regulaci\u00f3n del clima y resiliencia al cambio clim\u00e1tico<\/strong><\/p>\n<p>Uno de los principales aspectos que deben afrontar las sociedades urbanas en el siglo XXI es c\u00f3mo frenar sus emisiones de gases invernadero y adaptarse a los efectos ya presentes del cambio clim\u00e1tico. En Panam\u00e1 por ejemplo, uno de los efectos asociados al cambio clim\u00e1tico es el incremento de la temperatura absoluta, la cual podr\u00eda aumentar entre un 1\u00ba y 3 \u00baC, durante los meses en los cuales hay mayores temperaturas: abril y mayo (CATHALAC, 2008). Y los eventos de temperaturas m\u00e1ximas absolutas superiores a 38\u00baC ser\u00edan rebasados hacia el a\u00f1o 2020 (CATHALAC, 2008).<\/p>\n<p>En ciudades de climas calurosos, los episodios extremos de temperatura que se prev\u00e9n son de mayor gravedad debido a las condiciones adversas de base, asociadas al efecto de \u2018isla de calor urbana\u2019 (ONU-HABITAT, 2011). Un problema generado por la alta densidad de construcciones y materiales acumuladores de calor (hormig\u00f3n, asfalto, etc.), por la concentraci\u00f3n de actividades antr\u00f3picas generadoras de calor (tr\u00e1fico, climatizaci\u00f3n, etc.). De hecho, seg\u00fan los mapas de vulnerabilidad al cambio clim\u00e1tico de las distintas unidades ecol\u00f3gicas de Panam\u00e1, en lo referente a la temperatura, el \u00c1rea Metropolitana Pac\u00edfica (Panam\u00e1), tiene una vulnerabilidad media alta a cambios en el incremento de la temperatura (Tremblay &amp; Ross, 2007).<\/p>\n<p>Teniendo en cuenta que el aumento de temperatura de 1\u00baC supone un incremento de consumo energ\u00e9tico en la climatizaci\u00f3n de entre 3 y 4%, y puede llegar hasta un 10%, el consumo energ\u00e9tico podr\u00eda aumentar hasta un 30% con un incremento de temperatura de 3\u00baC.<\/p>\n<p>Para atenuar los efectos de la isla de calor y reducir los altos consumos energ\u00e9ticos es esencial la planificaci\u00f3n del arbolado como climatizador natural del microclima urbano.<\/p>\n<p>Las variables ambientales fundamentales para el confort t\u00e9rmico humano incluyen radiaci\u00f3n solar, temperatura en las superficies urbanas, temperatura del aire, humedad y velocidad del viento. Se ha demostrado en diversas investigaciones que la arborizaci\u00f3n urbana puede mejorar estas variables ambientales a trav\u00e9s de la prevenci\u00f3n de la radiaci\u00f3n solar y la reducci\u00f3n del calentamiento de las superficies de las edificaciones, que se suman el efecto reducci\u00f3n de la temperatura del aire a trav\u00e9s de la evapotranspiraci\u00f3n. (Akbari &amp; et al., 1992) (Simpson &amp; McPherson, 1996); (Georgi &amp; Zafiriadis, 2006). En resumidas cuentas, el arbolado urbano interviene en la modificaci\u00f3n del clima en zonas c\u00e1lidas, principalmente en los siguientes tres efectos (Akbari H. , 2002):<\/p>\n<p><em>Sombreado: <\/em>Las copas de los \u00e1rboles interceptan la radiaci\u00f3n solar evitando el calentamiento de las edificaciones, asfalto y pavimentos.<\/p>\n<p><em>Evapotranspiraci\u00f3n: <\/em>La transpiraci\u00f3n de las hojas, requiere energ\u00eda calor\u00edfica capturada del ambiente, produci\u00e9ndose un descenso de la temperatura en su entorno.<\/p>\n<figure id=\"attachment_33780\" aria-describedby=\"caption-attachment-33780\" style=\"width: 604px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/www.thenatureofcities.com\/2019\/12\/19\/tree-planting-in-green-urban-infrastructure\/dsc09510\/\" rel=\"attachment wp-att-33780\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-33780 size-large\" src=\"https:\/\/www.thenatureofcities.com\/TNOC\/wp-content\/uploads\/2019\/12\/DSC09510-747x560.jpg\" alt=\"\" width=\"604\" height=\"453\" \/><\/a><figcaption id=\"caption-attachment-33780\" class=\"wp-caption-text\">Las copas de los \u00e1rboles generan una pantalla protectora contra la radiaci\u00f3n solar, minimizando el efecto isla de calor en las ciudades. Foto: Graciela Arosemena.<\/figcaption><\/figure>\n<p>La capacidad del arbolado para la modificaci\u00f3n del clima urbano, sobre todo para la reducci\u00f3n de las altas temperaturas, depende fundamentalmente del grado de cobertura arb\u00f3rea, es decir el porcentaje de superficie urbana situada bajo la proyecci\u00f3n de la copa de los \u00e1rboles, as\u00ed como de la tipolog\u00eda y la densidad de las copas.<\/p>\n<p>Sobre el efecto refrescante de la vegetaci\u00f3n en ambientes urbanos, se ha reportado que mediciones hechas en distintas ciudades del Norte, tal como el estudio realizado en el parque zool\u00f3gico de Berl\u00edn (Hoerbert, 1982). En este estudio \u00a0las diferencias de temperatura fueron de 5-7\u00b0C y la humedad relativa variaba un 10%<a href=\"applewebdata:\/\/7709B4C7-F383-4D63-A959-7FEC91C00712#_ftn1\" name=\"_ftnref1\">[1]<\/a> y reporta variaciones de entre 3 y 8 \u00baC para distintas composiciones y especies de \u00e1rboles, las mediciones se hicieron tambi\u00e9n en distintas \u00e9pocas el a\u00f1o.<\/p>\n<p>Mediciones sobre el efecto de las sombras se han realizado en estudios en donde se valoraban dise\u00f1o, tipolog\u00edas de edificio, paisaje y climas, encontraron que el ahorro energ\u00e9tico estar\u00eda alrededor del 25% al 80%<a href=\"applewebdata:\/\/7709B4C7-F383-4D63-A959-7FEC91C00712#_ftn2\" name=\"_ftnref2\">[2]<\/a>. Los mayores ahorros fueron asociados con la densidad y extensi\u00f3n de las sombras, siendo la radiaci\u00f3n solar la mayor fuente de ganancias de calor (Simpson &amp; McPherson, 1996).<\/p>\n<p><strong>Conservaci\u00f3n de la biodiversidad y patrimonio natural<\/strong><\/p>\n<p>Desde una \u00f3ptica ambiental, los espacios abiertos urbanos, adem\u00e1s de ejercer funciones de control clim\u00e1tico, o de filtro para la contaminaci\u00f3n atmosf\u00e9rica, entre otros, debe garantizar la conservaci\u00f3n de la diversidad biol\u00f3gica, y una permeabilidad que permita las conexiones ecol\u00f3gicas, mantenido valores ambientales y paisaj\u00edsticos.<\/p>\n<p>Las ciudades pueden jugar un papel primordial en la conservaci\u00f3n de la biodiversidad a trav\u00e9s de estrategias que incluyen la introducci\u00f3n de ecosistemas y h\u00e1bitats en el tejido urbano, o la preservaci\u00f3n de los preexistentes, adem\u00e1s la creaci\u00f3n de espacios verdes urbanos continuos que garantice la conectividad biol\u00f3gica y controlen la fragmentaci\u00f3n territorial (Generalitat de Catalunya, 2002). Un objetivo fundamental de ello es establecer como elemento vertebrador del territorio una red continua de espacios naturales, que atraviese la ciudad y conecte los espacios naturales periurbanos con los espacios naturales urbanos.<\/p>\n<p>Es evidente la necesidad de aumentar la natura en la ciudad y fortalecer las conexiones entre la ciudad y su entorno, y una de las piezas claves para conseguirlo son las estrategias de arborizaci\u00f3n urbana, orientadas a proporcionar efectivamente h\u00e1bitat a especies de aves, mam\u00edferos principalmente. Los \u00e1rboles proveen h\u00e1bitat, refugio y alimento para la fauna local. Para garantizar una arborizaci\u00f3n que restaure la biodiversidad ecol\u00f3gica en las ciudades, debe escogerse especies vegetales nativas, las cuales son a las que la fauna est\u00e1 acostumbrada. De hecho, el uso de especies ex\u00f3ticas es una de las causas directas de amenaza de la biodiversidad y la conservaci\u00f3n de ecosistemas, junto con la destrucci\u00f3n de h\u00e1bitat.<\/p>\n<p>Por el contrario, las especies nativas de \u00e1rboles en ambientes urbanos proveen alimento a fauna, que ser\u00eda reducida o ausente en el caso de \u00e1rboles ex\u00f3ticos. Adem\u00e1s, \u00e1rboles nativos incrementan la riqueza y diversidad de fauna, con lo cual una estrategia importante de arborizaci\u00f3n urbana es el reconocimiento cu\u00e1les especies nativas de \u00e1rboles son h\u00e1bitat de determinada fauna, con tal de establecer un h\u00e1bitat biodiverso en el entorno urbano.<\/p>\n<figure id=\"attachment_33782\" aria-describedby=\"caption-attachment-33782\" style=\"width: 604px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/www.thenatureofcities.com\/2019\/12\/19\/tree-planting-in-green-urban-infrastructure\/img_3239-2\/\" rel=\"attachment wp-att-33782\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-33782 size-large\" src=\"https:\/\/www.thenatureofcities.com\/TNOC\/wp-content\/uploads\/2019\/12\/IMG_3239-2-747x560.jpg\" alt=\"\" width=\"604\" height=\"453\" \/><\/a><figcaption id=\"caption-attachment-33782\" class=\"wp-caption-text\">Parque Natural Metropolitano, en medio de la ciudad de Panam\u00e1. Bosque h\u00famedo a seco tropical reserva de biodiversidad que brinda servicios ambientales tales como actuar de esponja de agua lluvia y sumidero de gases contaminantes. Por todas estas funciones, debe ser considerado un equipamiento de la infraestructura verde de la ciudad. Foto: Graciela Arosemena.<\/figcaption><\/figure>\n<p><strong>Un nuevo modelo de espacios abiertos urbanos<\/strong><\/p>\n<p>El impacto que est\u00e1n generando los problemas ambientales, locales y globales, sobre los entornos urbanos no tienen precedentes en la historia urbana, lo cual amerita no solamente repensar la forma de planificar y construir ciudades, sino adem\u00e1s, es fundamental un nuevo planteamiento del sistema de espacios libres y verdes urbano. Es por ello que la ecolog\u00eda, biolog\u00eda y la climatolog\u00eda, son disciplinas que han adquirido una mayor relevencia en el paisajismo, en la planificaci\u00f3n y dise\u00f1o de espacios abiertos, para la configuraci\u00f3n de verdaderos equipamientos urbanos.<\/p>\n<p>Ninguna ciudad puede afrontar los retos ambientales del siglo XXI, sin considerar la construcci\u00f3n de una infraestructura verde ecol\u00f3gica.<\/p>\n<p><strong>Graciela Arosemena D\u00edaz<\/strong><br \/>\nPanama<\/p>\n<p>On <a href=\"https:\/\/www.thenatureofcities.com\" target=\"_blank\" rel=\"noopener noreferrer\">The Nature of Cities<\/a><\/p>\n<p>&nbsp;<\/p>\n<p><strong>Trabajos citados<\/strong><\/p>\n<p><strong>\u00a0<\/strong>Akbari, &amp; et al. (1992). <em>Cooling our communities: A Guidebook to tree planting and light colored surfacing. .<\/em> U.S.A EPA, Ofice of Policy Anallysis, Climate Change Division, Washington, D.C.<\/p>\n<p>CATHALAC. (2008). <em>Potential Impacts of Climate Change and Biodiversity in Central America, Mexico and Dominican Republic.<\/em><\/p>\n<p>Georgi, N., &amp; Zafiriadis, K. (2006). The Impact of trees on microclimate in urban areas. <em>Urban Ecosyst<\/em> .<\/p>\n<p>Hoerbert, M. (1982). A climatic and air hygienic aspects in planning of iner-city open spaces: Berliner Grosser Tiergartes. <em>Energy and Buildings<\/em> <em>, 5<\/em> (1).<\/p>\n<p>Naredo, J. (1997). Sobre el origen, eluso y el contenido del t\u00e9rmino sostenible. <em>Cuadernos de Guincho<\/em> .<\/p>\n<p>ONU-HABITAT. (2011). <em>Informe mundial sobre asentamientos humanos. Las ciudades y el cambio clim\u00e1tico: Orientaci\u00f3n para pol\u00edtcas.<\/em> Londres: Earthscan.<\/p>\n<p>Rueda, S (1995)\u00a0 Ecologia Urbana: Barcelona i la seva Regi\u00f3 Metropolitana com a referents. Ed. Beta Editoria<\/p>\n<p>Simpson, J., &amp; McPherson, E. (1996). Potential of tree shade for reducing residential energy use in California. <em>Journal of Arboriculture<\/em> (22).<\/p>\n<p>Sorensen, M., Barzetti, V., Keipi, K., &amp; Williams, J. (1998). <em>Manejo de las \u00e1reas verdes urbanas. Documento de buenas pr\u00e1cticas.<\/em> Banco Interamericano de Desarrollo. Divisi\u00f3n de Medio Ambiente del Departamento de Desarrollo Sostenible., Washington, D.C.<\/p>\n<p>Tremblay, L., &amp; Ross, E. (2007). <em>A Preliminary Assessment of Ecosystem Vulnerability to Climate Change in Panama.<\/em>McGill University and Smithsonian Tropical Research Institute, Panama.<\/p>\n<p>United States Environmental Protection Agency. (2016). <em>Green Infrastructure and Climate Change. Collaborating to Improve Community Resiliency.<\/em><\/p>\n<p>Vargas, K., McPherson, G., Simpson, J., Peper, P., Gardner, S., &amp; Et al. (2008). <em>Tropical Community Tree Guide. Benefits, Costs, and Strategic Planting.<\/em> United States Department of Agriculture. Forest Service. Pacific Southwest Research Station.<\/p>\n<p><strong>Notas<\/strong><\/p>\n<p><a href=\"applewebdata:\/\/7709B4C7-F383-4D63-A959-7FEC91C00712#_ftnref1\" name=\"_ftn1\">[1]<\/a>\u00a0 Mascar\u00f3, L. R. AMBI\u00caNCIA URBANA = URBAN ENVIROMENT. Sagra-D. C. Luzzatto, Porto Alegre, 1996.<\/p>\n<p><a href=\"applewebdata:\/\/7709B4C7-F383-4D63-A959-7FEC91C00712#_ftnref2\" name=\"_ftn2\">[2]<\/a>Meier, A.K. STRATEGIC LANDSCAPING AND ARI-CONDITIONING SAVINGS: A LITERATURE REVIEW. Energy and Buildings. 1990.<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Lea esto en espa\u00f1ol. The functions of today&#8217;s green are defined mainly by the needs that were conceived in the hygienist movement linked to the industrial city of the nineteenth century. Environmental pollution was the driving force behind public open spaces at that time, and at that time, the need for socialization and recreation was [&hellip;]<\/p>\n","protected":false},"author":644,"featured_media":33779,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[273,297],"tags":[401,73,55,84,27,90,168,62,449],"coauthors":[878],"class_list":["post-33777","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-essay","category-essay-science-and-tools","tag-biodiversity","tag-biophilia","tag-conservation","tag-livability","tag-south-america","tag-sustainability","tag-trees","tag-water","tag-wetlandsriversstreams"],"_links":{"self":[{"href":"https:\/\/www.thenatureofcities.com\/TNOC\/wp-json\/wp\/v2\/posts\/33777","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.thenatureofcities.com\/TNOC\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.thenatureofcities.com\/TNOC\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.thenatureofcities.com\/TNOC\/wp-json\/wp\/v2\/users\/644"}],"replies":[{"embeddable":true,"href":"https:\/\/www.thenatureofcities.com\/TNOC\/wp-json\/wp\/v2\/comments?post=33777"}],"version-history":[{"count":1,"href":"https:\/\/www.thenatureofcities.com\/TNOC\/wp-json\/wp\/v2\/posts\/33777\/revisions"}],"predecessor-version":[{"id":57158,"href":"https:\/\/www.thenatureofcities.com\/TNOC\/wp-json\/wp\/v2\/posts\/33777\/revisions\/57158"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.thenatureofcities.com\/TNOC\/wp-json\/wp\/v2\/media\/33779"}],"wp:attachment":[{"href":"https:\/\/www.thenatureofcities.com\/TNOC\/wp-json\/wp\/v2\/media?parent=33777"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.thenatureofcities.com\/TNOC\/wp-json\/wp\/v2\/categories?post=33777"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.thenatureofcities.com\/TNOC\/wp-json\/wp\/v2\/tags?post=33777"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.thenatureofcities.com\/TNOC\/wp-json\/wp\/v2\/coauthors?post=33777"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}