Compendium Vol. 3 No. 2: Adaptation and Urban Resilience

The industrialization that has built today’s splendid high-tech cities isolated us from the land and water sources of the materials fueling this progress. Our cities scarcely reveal that the oxygen we breathe, the food we eat, the purification of waters, and to some extent the bucolic weather patterns we have long relished have been gifts from the ensemble of living creatures on Earth interacting in the form of ecosystems. We urbanites have managed in this brief past couple of centuries – a small fraction of human history – to harbor an illusion of independence from nature.

With their hard, gray and angled surfaces, ravenous appetites, and continuous toxic waste streams, cities in general surrendered themselves as ecological sacrifice zones. Against a foe so powerful as the drive for industrial development, there was never much hope for nature’s cause in a city. Yet to those of us with the means, cities are treasure troves of excitement, intrigue, social interaction, pleasure, and comfort, and it has perhaps been worth the sacrifice.

Yet if the wholesale exchange of ecosystem services for techno-industrial services was largely affordable in the 20th century, the growing likelihood of suffering or dying from climate-change-induced extreme weather makes this bargain harder to swallow. We’ve reached a time of reckoning. Cities of the world are now on the front lines of increasingly severe hurricanes, floods, fires, heat waves, and sea-level rise, and are thus bearing witness to our inextricable ties to nature.

As home to more than half of humanity, though, cities are uniquely positioned to drive the transition needed to salvage civilization and life in general from real-time ecological collapse. As aggregators of consumption and waste production, cities have plenty of slack to tighten. As population centers, they have the most at stake. As weavers of diverse cultures bursting with talent and creativity, cities have the people power to discover effective solutions. And as localized political bodies, cities have the potential to be cohesive enough to make key policy changes that favor adaptation and resilience to climate change.

Many effective ways to enhance urban resilience are known. They are described in various schools of thought – ecological engineering, industrial ecology, green infrastructure, sponge cities, biophilia, reconciliation ecology, and urban ecology, for example, which all generally aim to bolster ecosystem services in and around human habitation. Methods involve restoring original ecosystems (such as wetlands, forest, prairie, floodplains, mangrove forests, river delta systems and oyster reefs) adjacent to cities, and creating ecologically functional green spaces within cities, such as vegetated roofs and walls, or wooded parks. The ecosystem services these features deliver are meant to replace or fortify industrial infrastructure serving similar purposes. Here are a few examples:

• Forested watersheds purify water for downstream consumers. For example, New York City compensates upstream watershed communities for protecting riparian forests and reducing agricultural runoff. These watershed investments totalling $1.5 billion over 10 years pale in comparison to the alternative of building a $6-billion dollar filtration system requiring additional annual operating and maintenance costs [Postel & Thompson 2005]. Globally, “restoring upland forests and watersheds could save water utilities in the world’s 534 largest cities an estimated $890 million each year and is critical for regulating water flows and managing the future’s more extreme floods” [Global Commission on Adaptation 2019: 31].  
• Salt marshes and coastal wetlands trap sediment to allow for coastal elevation rise in the face of sea-level rise, while also lowering erosion rates, and reducing wave strength in storms. “Properties behind a marsh, on average, save 16% in flood losses every year compared to properties where marshes have been lost,” according to a study of a coastal community in New Jersey hit by Hurricane Sandy in 2012 [Narayan 2017: 9463]. Coastal wetlands can even work in concert with nature friendly, grass-covered levees further inland by protecting the levees from wave damage [Cheong 2013].
• An oyster reef can reduce up to 95% of wave height; trap sediment allowing the shoreline to rise as sea level rises; protect shorelines from erosion; improve water quality through filtration; and support breeding ground for economically valued species, such as blue crab, red drums, flounder and spotted sea trout [Cheong 2013]. By contrast, sea-walls, which can also protect coastal cities from wave action, have the negative side effects of eroding neighboring shoreline and damaging surrounding ecosystems.
• A single full-grown tree has the cooling power of 10 air conditioning units [Kleerekoper 2012], and a patch of woods in a city can make even a broiling summer day feel fairly pleasant. Wooded areas of Washington DC are 17F degrees cooler than areas of the city with no trees on a hot summer day [NOAA 2018]. “For cities, an annual investment of $100 million in urban tree planting could create enough shade to cut average temperatures by 1°C for 77 million people around the world” [Global Commission on Adaptation 2019: 31].
• Green walls and green roofs cool buildings through shading, evapotranspiration and insulation (the soil layer of a green roof insulates the building), thus significantly reducing buildings’ energy demands. Green walls have been shown to lower adjacent air temperatures by 0.2C to 3C [Kleerekoper 2012, Cameron 2014].

These methods are immediately relevant as cities continue to grow: two thirds of humanity is projected to reside in cities by 2050 [Collas 2017]. Population growth and aging infrastructure require ongoing renovation and new construction. For example, the number of houses in the US grew by 1.2 million between 2017 and 2018 [US Census 2019]. Globally, an estimated 60% of the built environment will be new or replaced by 2050 [Ahern 2014].

Individual buildings and houses are not necessarily designed, however, with climate risk in mind. The American Institute of Architects has recently created a new standard that a building must be designed to withstand environmental conditions over its entire design life. That means that if an architect today takes on the design of a commercial building whose estimated life is 80 years, it must be designed for the expected climatic conditions of 2100. For example, if climate-projection maps show a likelihood of flooding in a particular location, then a new building site should be considered; if high winds are a projected risk then special attention should be paid to roof design. However, architects are not required to consider climate projections and in many cases rely solely on building codes, which are based on historical data sometimes decades old [The American Institute of Architects 2019].

In the rush to grow and in the absence of an ecologically informed planning and design framework, new construction often increases a city’s vulnerability to severe weather and puts people in harm’s way who might otherwise have been better protected. “In several coastal U.S. states, for example, the highest rates of home construction since 2010 have occurred in flood-prone areas” [Global Commission on Adaptation 2019: 39]. Tragically, “cities are building over floodplains, forests, and wetlands that could have absorbed stormwater or offered respite and precious water during heat waves and droughts” [Global Commission on Adaptation 2019: 39]. Globally, some cities lack even basic floodplain maps.

Tragically, “cities are building over floodplains, forests, and wetlands that could have absorbed stormwater or offered respite and precious water during heat waves and droughts” [Global Commission on Adaptation 2019: 39]. Globally, some cities lack even basic floodplain maps.

Why, when information grows daily about climate risk as well as effective methods to enhance resilience, is it too often not taken into account? The answer to this question certainly involves complex political, cultural and economic analyses. Yet more superficially, a barrier may simply be that ecology and climate are not well integrated into mainstream planning and engineering, and that various types of expertise are too often siloed, resulting in insights from urban ecology being “often overlooked in engineering, planning, and policy for any sort of urban future.” Likewise, “the technical and built aspects of cities are central to the very fabric of urban systems and, perhaps unintentionally, are often overlooked or ignored in social-ecological studies” [McPhearson 2016: 11].

Even climate-focused institutions tend to unnecessarily separate mitigation and adaptation objectives, rather than thinking holistically through how solutions could be multifunctional and mutually reinforcing. This current lack of integration results in suboptimal outcomes and scarce resources being inefficiently spent. By contrast,

With a synergetic approach, AFOLU [agriculture, forests, and other land use] projects would be designed to combine adaptation and mitigation in a way that project components interact with each other to generate additional climate benefits compared to projects in which adaptation and mitigation are separated. Mainstreaming climate compatible development (i.e., adaptation, mitigation, and development) may avoid that projects respond to adaptation and mitigation urgencies separately [Kongsager 2016: 279].

Similarly, urban ecologists argue for holistic and collaborative approaches to development in the face of climate breakdown. Multidisciplinary teams must work together

to facilitate understanding of how both green and grey infrastructure can be linked – and in the future, deeply integrated – to deal with urban challenges and meet the needs of urban residents [McPhearson 2016: 11].

In addition to greater inter-sectoral collaboration, a large body of generalized and transferable knowledge in urban ecology is still needed, given the relative newness of this field, for planners to more easily incorporate new perspectives into their work. Given the urgent need for ecologically informed development, however, Ahern et al. [2014] argue that urban planners could forgo future research results by taking an ‘adaptive design’ approach. This would involve working in multidisciplinary teams that “learn by doing,” and incorporate low-risk, experimental design features into urban development plans, monitor results, make adjustments, and share what they learn.

Professionals, planners and designers need to make decisions in response to approval and development schedules. However, the “traditional” professional timeframe mandates an “imperative to act” that relies on readily available, existing knowledge and established best practices – typically without the opportunity to conduct new research. This imperative tends to favor decisions based on existing knowledge, and to inhibit innovation. The challenge of providing ecosystem services for urban sustainability planning and design will rely on emerging urban planning and design theory and new knowledge in design and engineering. Transdisciplinarity, implying the co-production of knowledge by scientists, planning professionals and urban dwellers, is a key to realize the potential of this planning approach [Ahern 2014: 255].

Further stressing the urgency to mainstream ecological principles into development planning and engineering, Mitch and Jorgenson [2003: 372] state: “The idea of nature conservation is so important that it needs to become a goal of engineering, not just one of its possible outcomes.” These authors argue that any engineering plans that omit ecological considerations have no place in today’s ecologically devastated world.

“The idea of nature conservation is so important that it needs to become a goal of engineering, not just one of its possible outcomes” [Mitch and Jorgenson 2003: 372].

We build solid waste facilities and water pollution control systems and atmospheric emissions of the greenhouse gas methane result. We use industrial wastewater treatment methods to remove heavy metals from a factory and then must dispose of metal-rich sludge. We burn sludge and solid wastes and we create air pollution problems. We are moving materials around in a shell game—if it is not under one shell, it is under another [Mitsch & Jorgenson 2003: 374].

The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services reiterates this observation of the shortcomings of strictly human-built infrastructure and technology to deal with grave environmental problems.

People have created substitutes for some other contributions of nature, but many of them are imperfect or financially prohibitive. For example, high-quality drinking water can be realized either through ecosystems that filter pollutants or through human-engineered water treatment facilities. Similarly, coastal flooding from storm surges can be reduced either by coastal mangroves or by dikes and seawalls. In both cases, however, built infrastructure can be extremely expensive, incur high future costs and fail to provide synergistic benefits such as nursery habitats for edible fish or recreational opportunities. More generally, human-made replacements often do not provide the full range of benefits provided by nature [Diaz 2019: 13].

A great irony, as Carl Sagan once observed, is that as deeply divided as humanity is along nationality, political and class lines, not to mention professional specialization, the earth’s climate and ecosystems are deeply intertwined. What happens in Las Vegas or any other city does not stay in that city, but ripples out over the region and the globe. Likewise, how we manage landscapes upstream of and around a city significantly affects how badly battered it will be by the next big storm passing over it.

What the articles summarized below illustrate is that working with nature to boost ecosystem services to cities is eminently practical. Not only are ecological climate-change adaptation approaches highly effective as a protective buffer against severe weather; they also deliver several co-benefits – not the least which is mitigating the city’s impact on the rest of the planet by creating desperately needed wildlife habitat (at least for insects, birds and other small animals) and sequestering greenhouse gases. Urban green space also improves human health and wellbeing by reducing air pollution and providing islands of beauty and tranquility.

What’s exciting about the urban ecology opportunity is that more than half of us are perfectly situated to help shift the tide toward more ecologically coherent cities. Through collective action in shared spaces like schoolyards, churchyards or parks, even people without land of their own can restore ecosystems. Proponents for a “citizen science” model of grassroots engagement in conservation efforts [Francis & Lorimer 2011] note that urban areas have key advantages: (1) a large population base potentially available for training, implementation, monitoring and knowledge sharing related to ecosystem restoration; (2) concentrations of university and professional scientists with expertise to offer in grassroots and collaborative projects; and (3) high visibility of ecological urban adaptation efforts to generate enthusiasm and raise public awareness.

Francis and Lorimer [2011] further observe, however, that “motivation for conservation remains a major obstacle” and that “the biodiversity that emerges [from urban ecology efforts] is likely to be in untidy, unexpected and non-traditional forms” [Francis & Lorimer 2011: 1435] and that the management of expectations is therefore important. Perhaps, though, as the stakes continue to rise and to become clearer and more alarming to more and more people, the knowledge base already established on how to work with nature to better protect cities from climate change will be just enough to kick-start a paradigm shift in urban planning and development.

More generally, human-made replacements often do not provide the full range of benefits provided by nature [Diaz 2019: 13].

Compilation of article summaries on adaptation and urban resilience

Global change and the ecology of cities, Grimm et al. 2008

Whereas just 10 percent of people lived in cities in 1900, now more than half the global population is urban and that proportion continues to grow. Cities occupy less than 3% of the Earth’s land surface, but generate 78% of global CO2 emissions and consume 76% of wood used for industrial purposes.

Urban dwellers depend on the productive and assimilative capacities of ecosystems well beyond their city boundaries — “ecological footprints” tens to hundreds of times the area occupied by a city — to produce the flows of energy, material goods, and nonmaterial services (including waste absorption) that sustain human well-being and quality of life [Grimm 2008: 756].

The social and environmental costs of building and servicing the world’s wealthiest cities since the colonial period to the present has been enormous:

Although exacerbated by recent globalization trends, centuries ago the demands of European consumers led to deforestation of colonial lands and, more recently, demand for beef from countries of the Western Hemisphere has transformed New World tropical rainforests into grazing land [Grimm 2008: 756].

Because cities so radically transform landscapes, creating new and less functional ecosystems in the process, they were “shunned” by ecologists during the 20th Century, “with the result that ecological knowledge contributed little to solving urban environmental problems” [Grimm 2008: 756]. However, even though cities contribute disproportionately to the current ecological crisis, they are by the same token increasingly seen as a necessary part of the solution, both in terms of mitigating their effects, and withstanding and adapting to severe weather.

The field of “urban ecology” seeks to better understand the processes and patterns of urban ecosystems, with an eye toward boosting the ecosystem services within and around cities upon which urban dwellers depend. An observable pattern is the cycling of resources through a city. “The concept of urban metabolism analogizes a city to an organism that takes in food and other required resources and releases wastes to the environment” [Grimm 2008: 757]. Unlike natural ecosystems, though, which constantly recycle resources, urban ecosystems notoriously recycle little to nothing, and are therefore reliant on fresh extraction for the provision of new resources, while letting waste products accumulate as pollution.

Through an urban ecology lens, this discrepancy between natural and urban resource metabolism is duly noted and practical solutions proposed:

Cities are hot spots of accumulation of N [nitrogen], P [phosphorus], and metals and, consequently, harbor a pool of material resources. Could high-nutrient, treated wastewater substitute for commercial N fertilizers to supply crops and lawns with nitrogen, for example? [Grimm 2008: 757]

Similarly,

A small (but growing) proportion of the copper extracted globally is recycled, yet increasing the reuse and recycling of copper and other metals would do much to stem the rapid rise in demand from sources increasingly difficult to extract. Such reuse also would alleviate problems of metal accumulation in soils [Grimm 2008: 757].

Another tendency of urban ecosystems is to generate surplus heat, creating an urban heat island (UHI), due to reduced vegetation cover (thus, reduced cooling effects of evapotranspiration) and increased surface area absorbing solar energy (buildings, roads, etc.). This UHI effect in turn increases the use of air conditioning by 3-8% in the US, the additional energy use for which represents a positive feedback, which increases global warming. By contrast, increasing vegetation cover in cities reduces the UHI effect, while also removing greenhouse gases from the atmosphere, thus representing a negative feedback, which reduces global warming.

Another area of analysis in urban ecology involves water management (including channelization of streams and sewers, for example). The design of urban water systems is typically devoid of the ecosystem service provided by the waterways that urban systems replace, making cities vulnerable to flooding, drought and excessive pollution.

Among the most important modifications that affect streams in urban areas is increased impervious cover, which changes hydrology and funnels accumulated pollutants from buildings, roadways, and parking lots into streams [Grimm 2008: 759].

Yet,

Successful, ecologically based designs of novel urban aquatic ecosystems are becoming more common and exemplify stream-floodplain protection, retrofitting of neighborhood stormwater flow paths, and use of low-impact stormwater/water capture systems as creative solutions to urban stormwater management [Grimm 2008: 759].

Advancing urban ecology toward a science of cities, McPhearson et al. 2016

The study of urban ecology has grown rapidly over the past couple of decades as the planet becomes increasingly more urbanized. The field started as the study of ecology within the green spaces of cities, and has since evolved into a multidisciplinary approach to understanding the city itself as an ecosystem with interacting social, ecological and technical components.

A variety of social processes contribute to vulnerability to heat, including variation in social capital and legacies of disinvestment, which can affect vulnerability to heat waves. Furthermore, differences in intra-urban surface temperature can be as large or larger than urban-rural temperature differences, and a number of social-ecological-technical infrastructure interactions have been found to determine climate outcomes in cities. For instance, the dense distribution of tall buildings influences the spatial pattern of solar radiation intensity and duration and so influences air temperatures.^[3] The highly heterogeneous distribution of vegetation in cities is a primary determinant of heat exposure, which is often greater for poor, elderly, and minority segments of the population, who are often less able to cope [McPhearson 2016: 9].

With an ultimate aim of fostering resilience among the world’s ever-growing cities, urban ecologists envision a transdisciplinary, participatory “ecology for cities” approach that integrates research and practice. Such collaboration could result in the beneficial integration of gray and green urban infrastructure.

Traditional risk-avoiding engineering designs for infrastructure design focus on hard, resistant elements such as increased-diameter sewage pipes for stormwater management or tanks to store sewage. In contrast, more flexible, diverse, and ecologically based elements include green infrastructure such as parks, permeable pavement, swales or retention basins, or agricultural and vacant land sites in urban areas. Urban infrastructure therefore mediates the relationships between human activities and ecosystem processes and may exacerbate or mitigate human impact depending on how it is developed [McPhearson 2016: 11].

How to make a city climate-proof, Kleerekoper, van Esch & Salcedo 2012

“The geometry, spacing and orientation of buildings and outdoor spaces” [Kleerekoper 2012: 30], as well as the prevalence of hard surfaces and reduced amount of vegetation, strongly modify the micro-climate of urban areas compared to rural surroundings. Characterized by an increase in temperature, a phenomenon referred to as urban heat island [UHI] effect has multiple causes. This includes, for example:

• Absorption of short-wave radiation from the sun in low albedo (low-reflection/high-absorption) materials
• Absorption and re-emission of longwave radiation by pollution
• Heat released through combustion from traffic, heating and industries
• Reduction of wind speed and obstruction of sky view by buildings, resulting in lowered heat loss from street “canyons”
• Decreased evaporation due to a surfeit of impermeable surfaces

An increase in global temperature combined with UHI may have serious health implications including death. The heatwave of 2006 resulted in about a thousand heat-related deaths in the Netherlands and was rated fifth-worst natural disaster of that year. Cities can reduce the UHI effect with adaptive measures that combine vegetation, water, built form and material.

“Vegetation cools the environment actively by evapotranspiration and passively by shading surrounding surfaces that otherwise would have absorbed short-wave radiation” [Kleerekoper 2102: ]. Such methods include expanding urban forests/parks, street trees, private gardens, and green walls or roofs. “Vegetation has an average cooling effect of 1 – 4.7C that spreads 100 – 1,000m into an urban area, but is highly dependent on the amount of water the plant or tree has available” [Kleerekoper 2012: ]

Water cools by evaporation, or by transporting heat out of the city as does a river or stream. The cooling effect of water ranges from 1 – 30C to a distance of 30 – 35m, with stagnant water cooling the least and flowing and dispersed water (like a fountain) cooling the most. Water also cools through permeable pavement and water storage infrastructure that makes it available to trees for transpiration.

The built form of cities increases the UHI effect by reducing heat loss when tall buildings block the release of long-wave radiation back up toward the sky, while also blocking wind ventilation. While city form is hard to change, any new development can opt to reduce the height to width ratio of streets to allow better ventilation and heat loss. Slanted roofs also increase ventilation.

Lastly, the choice of building materials affects the UHI effect. Permeable materials facilitate evaporation and light/white (high albedo) materials reflect short-wave solar radiation, thus cooling the city. By contrast, “waterproof” and dark materials reduce evaporation and absorb short-wave radiation, thus contributing to the UHI effect. A simulation model for Sacramento, CA, showed a 1 – 4C drop in temperature from a city-wide increase in albedo (such as through white rooftops) from 25 to 40%.

Despite the existence of a substantial body of knowledge on the causes of and solutions to the UHI effect, the transfer of this knowledge to city planners is often lacking. Due to differences in aim, focus, and expression among the various actors in the city planning process, as well as the theoretical (rather than practical) nature of scientific studies discussing the UHI effect, communication about UHI-reduction design solutions can be a challenge. Furthermore, quantification is often lacking in terms of heat accumulation for a given area, maximum acceptable levels of heat, and the quantity of needed measures to reduce UHI (number of trees or square meters of green space, for example) .

However, certain cities like Stuttgart have developed spatial parameters in urban planning guidelines with respect to climate change. In California a cool-roof material with low thermal admittance has been introduced in the Building Energy Efficiency Standard regulation of the state. The city of Portland is creating a reference guide of pavement options for low-use traffic zones. The greening policy in Chicago and Edinburgh involves increasing the number of street trees, as well as species heterogeneity to ensure resistance to vegetal disease (given that species diversity limits pest infestation).

Mitigating New York City’s heat island with urban forestry, living roofs and light surfaces, Rosenzwieg et al. 2006

Urban heat islands are created when solar energy is absorbed by non-reflective, impervious, and often rather dark surfaces, such as asphalt, stone, metal, and concrete, which are ubiquitous in cities. Exacerbating this solar energy absorption effect are abundant amounts of heat released from vehicles, factories and air conditioners, for example, as well as pollutants trapped in the lower troposphere that slow down the cooling of rising air.

In New York City, where this study was conducted, the “summertime nocturnal heat island averages 7.2ºF (4ºC). This means that during the summer months the daily minimum temperature in the city is on average 7.2ºF (4ºC) warmer than surrounding suburban and rural areas” [Rosenzwieg 2006: 1]. The authors tested the cooling effects of tree plantings, living rooftops and high albedo (light colored) surfaces, and found that curbside tree plantings were the most effective form of cooling per unit area, followed by living rooftops. High albedo (light/white) surfaces were the least effective at cooling per unit area, but were the most effective overall “because 64% of New York City’s surface area could be redeveloped from dark, impervious surfaces to lighter high-albedo surfaces” [Rosenzwieg 2006: 3], whereas only 17% of the city’s surface could be planted with new street trees.

—^[4]

The interaction of rivers and urban form in mitigating the Urban Heat Island effect: a UK case study, Hathaway & Sharples 2012

Like vegetative and light or reflective surfaces, water bodies have a cooling effect on cities, reducing the Urban Heat Island effect. The average temperature at the river in this study was 1C less than at a reference point elsewhere in the city. Furthermore, the form of the landscape on the banks of an urban river can either propagate (increase) or diminish the cooling effects of the river. This study found that vegetated river banks increased the cooling effect of the river by a difference of 2C compared to river banks covered in hard engineering materials (concrete/asphalt), while opening river banks (rather than enclosing them with buildings or walls) permitted significant cooling effects to be felt up to a distance of 30 meters from the river.

Overall, the results indicate that high levels of vegetation next to the river increase the cooling on the bank, that opening up the streets to the river increases the propagation of cooling and that the surface nature of the surrounding materials [e.g. vegetation versus concrete] can have a more significant effect on the air temperatures than the presence of the river [Hathaway & Sharples 2012: 20].

Overall, the results indicate that high levels of vegetation next to the river increase the cooling on the bank, that opening up the streets to the river increases the propagation of cooling and that the surface nature of the surrounding materials [e.g. vegetation versus concrete] can have a more significant effect on the air temperatures than the presence of the river [Hathaway & Sharples 2012: 20].

Urban development, land sharing and land sparing: the importance of considering restoration, Collas et al. 2017

With 66% of the world’s population predicted to live in cities by 2050, the challenge of reconciling urban growth with biodiversity conservation demands attention.

Although the environment is altered by urbanization, there is potential for cities to support a great deal of biodiversity [Collas 2017: 1866].

This study shows that urban growth and biodiversity enhancement are compatible by increasing housing density (in order to reduce total surface area of development) while restoring ecosystems on remaining green space through woodlot plantings. The study was conducted in Cambridge, England, whose population is expected to grow by 22% between 2011 and 2031, and where “current green space supports relatively few trees” [Collas 2017: 54]. Green space could be maximized and restored to woodlots while additional high-density housing could accommodate the expected population growth.

Furthermore, only 2% of green space (i.e. ≥30 ha) is needed for conversion to woodlot to increase the native tree population size in Cambridge while also increasing high-density housing. This is compared to an alternative growth scenario, where new development is low-density and inhabitants are expected to plant trees in their relatively large yards, while no city-led green space ecosystem restoration occurs.

In conclusion, the authors offer this:

For other cities in the UK and across Europe, which have generally long been cleared of natural habitat, restoration in parallel with the expansion of higher density housing would appear to offer greatest scope for accommodating population growth at least cost to nature. This would require policy and economic incentives to directly link high-intensity human land-use to large-scale restoration [Collas 2017: 1871].

Promoting and preserving biodiversity in the urban forest, Alvey 2006

Given the dangerous, precipitous global decline in biodiversity, coupled with rapid urbanization, cities have a key role to play in protecting biodiversity. In fact, cities already do harbor a large share of biodiversity. This may be due to the fact that cities are often situated in places of large inherent biodiversity (along rivers, for example), and/or because of large numbers of introduced species and landscape heterogeneity in cities. Furthermore, surrounding agricultural areas are often simplified landscapes with limited biodiversity while many forests are degraded, and thus less biodiverse, due to timber harvest regimes, roads, etc. Thus, contrary to what might be assumed, rural areas are not necessarily more biodiverse than cities.

The author stresses the importance of managing cities to increase biodiversity. This process should begin with a city-wide tree inventory to identify tree species, locations and health. Management should focus on increasing biodiversity among street trees, and in parks, woodlots, abandoned lots, and back/front yards, while also fostering public awareness and appreciation for ecological principles. Planting efforts should prioritize native species, which are better adapted to local conditions, are non-invasive, and whose protection contributes to global biodiversity conservation. (While great numbers of introduced species may increase local biodiversity, it has a homogenizing effect on global biodiversity.) Furthermore, natural regeneration of parks and woodlots should be encouraged through less intensive management, whereby seeds of native (or at least non-invasive) species are allowed to germinate and establish where they fall, instead of being fastidiously mowed or weeded.

A new vision for New Orleans and the Mississippi delta: applying ecological economics and ecological engineering, Costanza, Mitsch & Day 2006

What happened in New Orleans [during Hurricane Katrina], while a terrible “natural” disaster, was also the cumulative result of excessive and inappropriate management of the Mississippi River and delta, inadequate emergency preparation, a failure to act in time on plans to restore the wetlands and storm protection levees, and the expansion of the city into increasingly vulnerable areas [Costanza, Mitsch & Day 2006: 467].

Mismanagement here refers to damming, leveeing and canal dredging of the Mississippi River Delta, resulting in a significant loss of wetlands and the erosion of barrier islands over the past 100-plus years. Coastal marshes and barrier islands depend on regular inputs of sediments deposited by the river, which has been isolated from the delta plain and unable to thus nourish it. Two thirds of the river empties directly into the depths of the Gulf of Mexico, while one third empties into shallow waters, where it nourishes wetlands via the Atchafalaya, the river’s single remaining distributary (other distributaries having been closed off).

Damage from Hurricane Katrina was exacerbated by its prior loss of wetlands. Expansive coastal wetlands protect coastal communities from hurricanes by “decreasing the area of open water (fetch) for wind to form waves, increasing drag on water motion and hence the amplitude of a storm surge, reducing direct wind effect on the water surface, and directly absorbing wave energy” [Costanza, Mitsch & Day 2006: 468].

For the rebuilding of New Orleans after the hurricane, the authors recommended several core principles aimed at social and ecological resilience. Among their recommendations, they advise that areas of the city currently below sea level (by as much as 5 meters in some parts) not be rebuilt, but, rather, be restored to wetland. This would allow for temporary water storage within the city, water filtration, and biodiversity protection. They also suggest the reopening of distributaries and the controlled breaching of certain levees to allow the river to resume its ancient task of distributing sediment over a greater expanse of coastal marshes, allowing these marshes to gradually rise in step with sea level rise.

Eco-engineering urban infrastructure for marine and coastal biodiversity: which interventions have the greatest ecological benefit? Strain et al. 2017

While the majority of people on Earth live in cities, the majority (60%) of the world’s largest cities are located within 100 kilometers of a coast. The pollution and urban infrastructure (such as marinas, sea walls, or oil/gas platforms) emanating from cities greatly stresses coastal marine habitats. Coastal infrastructure tends to be vertical and smooth, offering little or nothing in the way of habitat niches or physical protection for various marine organisms. An eco-engineering approach to improve habitat quality and increase biodiversity is the addition of textural features, such as ledges, small holes, basins or crevices to the hard surfaces of urban marine infrastructure.

As predicted, overall microhabitat-enhancing interventions had a positive effect on the abundance and number of species across the studies. Nevertheless, the magnitude of their effects varied considerably, from zero to highly positive according to the type of intervention, the target taxa, and tidal elevation [Strain 2017: 434].

In the intertidal^[5], interventions that provided moisture and shade had the greatest effect on the richness of sessile^[6] and mobile organisms, while water-retaining features had the greatest effect on the richness of fish. In contrast, in the subtidal^[7], small-scale depressions which provide refuge to new recruits from predators and other environmental stressors such as waves, had higher abundances of sessile organisms while elevated structures had higher numbers and abundances of fish. The taxa that responded most positively to eco-engineering in the intertidal were those whose body size most closely matched the dimensions of the resulting intervention [Strain 2017: 426].

Coastal adaptation with ecological engineering, Cheong et al. 2013                      

Because of the multiple threats and uncertainties of a changing climate, protecting coastal areas simply by building new seawalls (or some other such inflexible, single-tactic approach) is unlikely to be the most effective option. Instead, combined coastal adaptation strategies to allow for a dynamic response to multiple stressors are increasingly preferred. Climate scientists and coastal managers are mainstreaming inclusion of climate change into an Integrated Coastal Zone Management framework, aimed at promoting the activities of the different coastal sectors by coordinating government agencies and private participation.

Contrary to a “regret-risking option,” a no- or low-regret option is adopted to generate a net social benefit irrespective of the future outcome of climate change. Revamping early warning systems, preventing land reclamation, improving housing and transportation, capacity development in education, poverty reduction, and efforts to build resilient ecosystems are examples of a low- or no-regret options.

Traditional engineering, while sometimes protective of coastal communities, has undesired effects, such as eroding non-target, neighboring coastline and destroying adjacent ecosystems. By contrast, eco-engineering tools emphasize positive interactions among species that boost ecosystem productivity and stability, and therefore the strength of the ecosystem to withstand and buffer heavy storms, thus protecting coastal communities.

For example, sea-grasses planted with clams at their roots grow faster and in turn increase total fixed carbon. Oyster reefs attenuate up to 95% of wave height, control turbidity by removing algae, bacteria, and suspended organic matter, improve water quality through their filtration capacity, and enable seafood supply and thus job creation and recreation. Oyster reefs also support breeding ground for economically valued species, such as blue crab, red drums, flounder and spotted sea trout.

In mangroves, transplants planted in close proximity rather than the traditional spread pattern allows for a shared benefit of positive interaction that enhances plant growth and biodiversity. Restored mangrove ecosystems alleviate the impact of moderate tsunami waves, while the roots trap sediment and elevate the land surface, allowing for adaptation to sea-level rise. Intact mangrove also provides local employment as well as breeding grounds for fish.

Marshes dampen wave actions and reduce shoreline erosion, increase fish production, and are compatible with levee designs on the marshes’ landward edges that are nature-friendly. In the Netherlands, for instance, levees built to prevent flooding during storms were covered with thick grass to maintain their integrity, while the seaward marshes reduce the levees’ exposure to wave action; grasses were then grazed by sheep to provide milk and meat for consumption.

The synergy of ecology and engineering is key to addressing uncertainties related to climate-induced stressors. The combination of traditional and eco-engineering approaches coupled with the evaluation to measure the effectiveness of eco-engineered structures facilitate better decision making and prioritization of options.

Where we stand: climate action, The American Institute of Architects (AIA) 2019b

Noting that 40% of carbon emissions in the US come from the construction (including sourcing of materials) and operation (heating, cooling, lighting) of buildings and houses, the AIA pledges to achieve zero-carbon construction and operation of all new buildings, and retrofitting of existing buildings to reduce their energy use and increase their resilience to severe weather. They will achieve these goals through education, policy advocacy, calling for zero-carbon building codes, and advocating for the reuse of historic buildings rather than new construction.

Living Building Challenge Standard, June 2019

The construction and operation of buildings and houses is a major source of pollution and ecosystem destruction around the world. In light of this, the Living Building Challenge invites people to reimagine the built environment as a source of social and ecological regeneration.

Nothing less than a sea change in building, infrastructure and community design is required. Indeed, this focus needs to be the great work of our generation. We must remake our cities, towns, neighborhoods, homes and offices, and all the spaces and infrastructure in between. This is part of the necessary process of reinventing our relationship with the natural world and each other—reestablishing ourselves as not separate from, but part of nature, “because the living environment is what really sustains us” (E.O. Wilson) [International Living Future Institute 2019: 8].  

To that end the Living Building Challenge invites us to collaborate in building houses and buildings – or adapting existing ones – to have a positive, rather than simply less-negative, impact on the social and ecological systems where they are situated. The initiative runs educational and certification programs with several high standards, including, for example:

• Projects must be observant of and responsive to the local ecological and social context of the sites, and onsite landscaping must seek to emulate local ecosystem function.
• Access to locally grown food should be assured through onsite production and/or connection to local farms.
• The site must ensure adequate habitat for local species.
• Living Building Challenge designers must find ways to encourage pedestrian, bike and public transport options, while discouraging individual car travel.
• Water should be harvested and wastewater treated onsite using living or natural/non-chemical systems.
• Buildings/houses should supply their own energy on site (not through combustion), monitor their energy use, and minimize use through conservation.
• Construction materials should be salvaged or sustainably and transparently sourced, and non-toxic.
• In the interest of human wellbeing and social equity designs should allow natural light, beauty and comfort in the interior of the building, while the exterior must be accessible and welcoming to all members of the public, regardless of socioeconomic status.

Adapt now: a global call for leadership on climate resilience, Global Commission on Adaptation, September 2019

This report, led by Ban Ki Moon (UN), Bill Gates (Bill & Melinda Gates Foundation) and Kristalina Georgieva (World Bank), calls on decision makers worldwide to facilitate coordinated action to help communities adapt to climate change. Importantly, the report makes the case for nature-based adaptation approaches, which inherently help mitigation efforts as well. Adaptation measures are much cheaper than recovery and rebuilding: every $1 invested in adaption yields $2-10 (or more by some estimates) in avoided losses and other economic benefits (such as improved crop yields), as well as social and environmental benefits.

Despite a clear global imperative for rapid adaptation planning and action to be taken at local, regional and national levels, action is desperately lagging. The report cites four reasons for inaction: (1) broad failure to internalize climate change risk in everyday decision making; (2) human tendency to prioritize short-term planning at the expense of long-term goals; (3) lack of cross-sector collaboration, which leads to fragmentation of responsibility; and (4) lack of power/voice among those most affected by climate change.

The report succinctly articulates the value of working with nature to adapt to climate change, while highlighting the extent to which this vital information is neglected.

We can already see the immense opportunity of using nature to increase societal resilience in landscapes ranging from uplands to the ocean. Restoring upland forests and watersheds could save water utilities in the world’s 534 largest cities an estimated $890 million each year and is critical for regulating water flows and managing the future’s more extreme floods. Meanwhile, lakes, marshes, and river floodplains both slow the release of floodwater and filter out sediment. The Netherlands has harnessed these capabilities with a Room for the River strategy that increases capacity of rivers and their floodplains to hold floodwaters, reducing damage and loss of life.

Ecosystem restoration also is a powerful tool for feeding the hungry, cooling sweltering cities, and protecting communities. One striking example is farmer-led reforestation in the Maradi and Zinder regions of Niger, which has boosted crop yields, improved soil fertility, and lifted communities out of poverty. Tree cover has soared ten-fold and the daily time spent gathering firewood—a task that mainly falls to women—has dropped from 3 hours to 30 minutes. For cities, an annual investment of $100 million in urban tree planting could create enough shade to cut average temperatures by 1°C for 77 million people around the world. Restoring the mangrove forests that offer protections from rising seas and storm surges is two to five times cheaper than building engineered structures like underwater breakwaters, while also storing carbon and improving water quality and local fisheries.

Yet despite the powerful case for working with nature to reduce climate risks, the world has barely begun to realize this potential. Few governments have adopted these approaches widely, even though many cite natural solutions in their NDCs. And only 3 percent of nearly 2,000 companies reported using natural ecosystems as part of their climate adaptation strategies. The barriers include lack of awareness of the critical role of natural assets in underpinning social and economic resilience and lack of accessible funds to invest in nature-based solutions. In addition, the piecemeal way adaptation is often planned and executed undervalues or ignores the many benefits of working with nature.

Humanity faces a stark choice: We can harness nature-based solutions to mitigate climate change and to better adapt—or we can continue with business as usual and lose the essential and myriad services nature provides [Global Commission on Climate Adaptation 2019: 31]. 

To encourage adoption of nature-based adaptation strategies, the report recommends three steps: (1) raise the level of understanding of the value of nature for climate adaptation; (2) embed nature-based solutions into adaptation planning and policy; and (3) increase investment into nature-based solutions. Indeed, it is precisely the aim of Biodiversity for a Livable Climate and its compendium series to elevate the level of understanding and appreciation for nature-based adaptation and mitigation solutions to the climate crisis.

Yet despite the powerful case for working with nature to reduce climate risks, the world has barely begun to realize this potential. Few governments have adopted these approaches widely, even though many cite natural solutions in their NDCs. And only 3 percent of nearly 2,000 companies reported using natural ecosystems as part of their climate adaptation strategies. The barriers include lack of awareness of the critical role of natural assets in underpinning social and economic resilience and lack of accessible funds to invest in nature-based solutions. In addition, the piecemeal way adaptation is often planned and executed undervalues or ignores the many benefits of working with nature. Humanity faces a stark choice: We can harness nature-based solutions to mitigate climate change and to better adapt—or we can continue with business as usual and lose the essential and myriad services nature provides [Global Commission on Climate Adaptation 2019: 31].