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Many major urban areas are constrained with the amount of green space they can provide to residents. Encouragingly, building rooftops have emerged as a solution to fill this shortfall of urban green space.

Published January 1, 2004

By Peter Coles

The common image of cities as hot spots of crime and grime may need updating. They also can be havens of natural and cultural diversity – and could hold the keys to sustainable development in the 21^st century.

While some 3.2 billion people – half the world’s population – are now estimated to live in towns and cities, with a growing number of poor, “urban” is by no means incompatible with “nature,” even in a major city like New York. Once rare, peregrine falcons now nest on Manhattan bridges, while a survey carried out by the Brooklyn Botanic Gardens found over 3,000 species of plants in a 30-mile radius of the city – far more than in the vast cornfields of the Midwest.

The Need for Preservation

And, while the presence of man has driven some species of plant and animal close to extinction, cities may now be the only places they are still found. Paradoxically, they will no longer survive without human intervention to preserve them.

These topsy-turvy ideas emerged during a meeting at The New York Academy of Sciences (the Academy) in October 2003, entitled “Urban Biosphere and Society: Partnership of Cities,” co-organized with CUBES (Columbia University-UNESCO Joint Program on Biosphere and Society) and UN Habitat.

For many people, the built-up environment is the antithesis of nature, as Rutherford Platt, of the Ecological Cities Project at the University of Amherst, pointed out. “Nature” is somewhere else, outside the city, in a national park or some remote wilderness. But, recalling Lewis Mumford, champion of the green belt, he emphasized that not only can nature be part of a city, but cities themselves can be as much a part of nature as an anthill or a beaver colony.

Creating New Types of Habitat

Ecologists are now appreciating that cities, as well as preserving rare patches of ancient flora and fauna in parks and settler cemeteries, also present challenging new habitats, with their own adapted plants. “We are creating types of habitat that have never been seen before,” said Charles Peters, Kate E. Tode Curator of Economic Botany at the New York Botanical Garden, “like a vacant lot with 35 minutes of sunlight a day. It’s an interesting niche.”

Peters, who has been studying a 40-acre swathe of ancient oak and hickory forest in the Botanical Garden for several years, also defended the invasive species that are settling there, filling niches left by native species that have failed to adapt to an urbanized habitat. “The most important thing is that these plants continue to function, whether they’re from China or Siberia. We can’t put the forest back the way it was 200 years ago. To do that, we’d have to put the Bronx back the way it was 200 years ago. Forests are continually changing. What’s important is that the new species are controlling erosion, providing nutrients for the soil, recycling the air.”

Others argue that intact, native ecosystems, like the remnants of oak woodlands and prairies in Chicago, have a far richer biodiversity than those colonized by invasive species, and are more sustainable. Since 1996, Chicago Wilderness, a loosely-structured coalition that today comprises over 165 associations, institutions and organizations, has been working to restore biodiversity in the Windy City, which is visited by some 6 million neo-tropical birds every year on their way to and from Canada.

Retaining Residents

Chicago’s city fathers, explained John Rogner, Chicago Field Supervisor of the Fish and Wildlife Service of the Department of the Interior, bought patches of oak woodland and prairie to prevent them being developed. Their argument was that a beautiful environment, with access to nature, would stop residents – the city’s life force – from moving away.

After three years of research, including “bio blitzes” in which local residents and children help scientists count species, Chicago Wilderness established a “biodiversity recovery plan.” With a wide range of projects, such as ridding the oak woodlands of tenacious, but non-native buckthorn, the consortium is also helping to restore brown-field sites, like Calumet, south of the city, which ironically contains several endangered and critical species of bird, surviving amid the derelict steel plants and toxic waste dumps.

Mark Wigley, interim dean of the Graduate School of Architecture at Columbia University, suggested that for most people “old cities are the heroes, and new cities are the villains.” But this idealized image leaves out the crime, open sewerage, disease and overcrowding characteristic of city life in the Middle Ages.

For Robert Pirani, director of environmental programs for the New York Regional Plan Association, the “villain” today is not so much the post-industrial downtown as it is suburban sprawl. In the past 10 years, he said, land use in the New York area has expanded by 100%, while population has increased by less than 10%.

Sprawling Cities

This means “thousands of homes surrounded by lawns, and shopping malls surrounded by parking lots,” he said. According to Rutherford Platt, this trend can be seen across the U.S., where suburban population has increased fourfold since 1950, compared to an 85% increase in population. And, he added, car ownership in the U.S. has risen by 100% since 1970, while population increased by 40%. In Atlanta, which has been dubbed “sprawl city,” drivers spend an average of 72 hours a year in gridlock, he said.

If sprawl is a middle-class phenomenon in developed countries, however, it is associated with poverty in much of the south. While 82% of Brazil’s population live in cities, said Rodrigo Victor, of the São Paulo Biosphere Reserve, some 23% of the population of São Paulo live in shanty towns, mostly on the edge of the Green Belt Biosphere Reserve that surrounds the city, a part of the Atlantic Forest Biosphere Reserve.

With a global trend towards urban living – two-thirds of world population in 2030 will live in cities – the challenge is to find sustainable solutions to urban growth. One approach, according to freelance journalist Helen Epstein, is through architecture itself.

A new generation of high performance buildings attempt to behave more like natural systems, with water management on site, passive solar energy production, natural lighting and ventilation reducing their “footprint,” or impact on limited natural resources. An example is the Solaire housing development in Battery Park City, Manhattan. But, as architect Ernie Davis, mayor of Mount Vernon, New York, pointed out, these buildings are not usually for the poor, whereas project housing, which is designed to look as though it’s for the disadvantaged, does not have advanced design features.

Green Rooftops in South Korea

Green rooftops also offer a solution, as Kwi-Gon Kim, professor of landscape architecture at Seoul National University, South Korea, demonstrated. With 42% of Seoul covered by buildings, landscaping rooftops could add an estimated 200 square kilometers of green space to the city, about 30% of the Seoul area. In an experimental green roof project on top of UNESCO’s downtown Seoul office, just five months after its construction the 75 species of plant introduced at the outset had been joined by an additional 39 species, presumably from surrounding green belt areas, while 37 species of insect had colonized the site.

Seoul was one of 11 cities invited by CUBES to prepare case studies to see whether, and how, the UNESCO “biosphere” model could be applied to urban areas. This model, designed 30 years ago, has since been applied in 440 UNESCO Man and the Biosphere (MAB) sites in 97 countries. These are areas of terrestrial and coastal ecosystems that promote the conservation of biodiversity with its sustainable use.

They are internationally recognized, nominated by governments, and remain under the sovereign jurisdiction of the states in which they are located. Usually, they consist of a “core” area that has minimum human impact, surrounded by a “buffer zone” and a “transition” area, with increasing levels of social and economic activity, respectively. But, while some of the sites adjoin cities (like São Paulo), to date there is no urban biosphere site as such.

A Future Urban Biosphere Site

Cape Town, South Africa, which is already surrounded by three natural biosphere reserves, gives some clues as to what a future urban biosphere site might look like, although it is just a theoretical case study at this stage. As Ruida Stanvliet, of the Western Cape Nature Conservation Board illustrated, the nine provinces in the region house 3.5 million people, some of them affluent and white, living in suburbs, while much of the black population lives in extreme poverty, in temporary housing and with a high incidence of HIV/AIDS. Nonetheless, the area boasts a rich biodiversity, with some 9,000 plant species.

“Environment conservation is crucial for poverty alleviation,” said Stanvliet. “It connects people to their sustainable resource base.” And in Cape Flats, one area in the Cape Town urban biosphere case study, over 20% of the people live in sprawling, informal settlements. In some communities, 70% live with less than $1 a day, and only 36% of adults are in paid employment.

The windswept mosaic of dunes and wetlands of Cape Flats is where victims of apartheid were relocated. Now, in a pilot initiative, the City of Cape Town has joined with the Botanical Society of South Africa, the National Botanical Institute and the Table Mountain Fund, to form Cape Flats Nature. This project focuses on conservation and restoration of biodiversity in several sites, enlisting the participation of local people through educational programs.

The Cape Flats Nature project has a certain resonance with the Chicago Wilderness brown-field development in Calumet, half way across the globe from Cape Town. This linking of cities, at least informally, was one of the ambitions of the Academy/CUBES meeting.

As Many Questions as Answers

The meeting raised as many questions as it answered, but that was another of its ambitions. In a city like New York, where would the “core” of a biosphere site be? For William Solecki, of the Department of Geography at Hunter College, City University of New York, it could be the harbor and estuary area, which is historically the focus of human activity in the city, while pockets of intact wetland survive in adjacent Jamaica Bay.

And the “buffer zone” might be the watershed in the Catskills that feeds the “core.” Indeed, as Christopher Ward, commissioner of the New York City Department of the Environment explained, New York was able to avoid spending millions of dollars on a new water treatment plant by investing in protection of the watershed.

This inclusion of more distant areas in the biosphere of a city like New York is a way to acknowledge that its “footprint,” unlike that of an equivalent natural area, can even extend thousands of miles. The coffee consumed in New York has a direct impact on plantations as far away as Bolivia, which, incidentally, is where some of the migrant warblers come from that feed in Central Park every May and October. Food for thought.

Also read:  The Impact of Climate Change on Urban Environments

About the Author

Dr. Peter Coles is a freelance science writer and photographer living in Paris, France.

Advances in a new technique known as carbon capture will be critical as carbon-based energy supplies continue to be used around the world.

Published June 1, 2003

By Chris Michaud

How long can earth’s carbon-based energy supplies be sustained in the face of rising global demand? Can the environmental challenges that such energy sources pose be effectively mitigated?

To address these questions, Columbia University Professor Klaus S. Lackner told an April 17, 2003, Environmental Sciences Section gathering at The New York Academy of Sciences (the Academy) it is necessary “to destroy some preconceived notions.”

“Our problem is not that we are running out of energy,” Lackner told the audience. Rather, he posited that the problem lies in finding environmentally acceptable means of utilizing existing carbon resources to meet the world’s rising energy requirements. “Whether we like it or not,” he said, “we will have to look at carbon as a resource, see whether we have enough of it, and use that for the foreseeable future – in an environmentally acceptable manner.”

Now the Ewing-Worzel Professor of Geophysics at Columbia’s Earth Institute, Lackner’s opinion is based on 18 years of research at the Los Alamos National Laboratory, in New Mexico, where he worked on finding environmentally acceptable technologies for the use of fossil fuels. Fossil fuels provide 85 percent of all energy used in the world today. Contrary to common popular belief, Lackner said carbon-based resources continue to be both plentiful and relatively inexpensive.

Noting that the level of atmospheric carbon dioxide has risen from about 315 parts per million in 1958 to about 370 parts per million today, Lackner said the dilemma lies in the fact that “fossil carbon has caused environmental problems that need to be fixed,” adding that “we really cannot go on like that indefinitely.”

Demand for New Energy Innovations

Nevertheless, he noted that the continuing global desire for economic growth and development demands new energy innovations. Displaying a series of detailed charts and graphs showing historical energy consumption and GDP (gross domestic product) projections for the coming decades, Lackner said, “we are clearly creating an enormous shortage” by removing fossil carbon energy sources from the energy picture.

Due to increasing evidence of global climate change, Lackner said many people now believe the world must reduce its reliance on carbon energy sources. Adding credence to this argument is the “common wisdom,” which holds that “these are finite resources and we are bound to run out – it’s just a question of time.” Although “strong arguments have been made that we might run out of oil,” Lackner said, “that is not the same as running out of carbon,” and noted that coal reserves are plentiful.

The ultimate answer, Lackner said, lies in capturing carbon dioxide and utilizing the carbon resource without allowing excess carbon to escape into the atmosphere where it stays for about 100 years, possibly driving climate change.

The current challenge, he added, is “the technology issue of capturing carbon dioxide and putting it away, if for no other reason than there’s a huge resource sitting out there, and even if we try to be good about it and not use it, the temptation will be there until the day when we find another energy option that is even cheaper.”

Solutions

Using the world’s oceans for carbon deposits is not feasible, Lackner added, because carbon dioxide, an acid, changes the oceans’ pH level. And energy conservation, while laudable and helpful, is not going to solve the energy problem alone. In addition, it is difficult and expensive to collect carbon dioxide emitted by mobile sources, such as cars and airplanes, which generate a significant proportion of it. “We have a gap,” Lackner said, and new ideas and technologies are needed soon – within the next two decades.

Lackner proposed a couple of solutions: one is an artificial tree, a giant carbon-capturing device that he amusingly described as looking like a goal post covered with Venetian blinds; the other one is designed as a huge cooling tower. While the designs are still in an “early exploratory stage,” with various versions looking vastly different from each other, he said they all essentially aim to collect carbon dioxide directly from the air using wind as the transport agent.

Capture from air is rarely considered a viable option because carbon dioxide in the air is very dilute, a seemingly huge obstacle, but Lackner believes the technologies capable of capturing more dilute substances can be developed. He hopes for a pilot demonstration of one of the devices, which could lead to its commercial manufacture and implementation.

A Radical Alternative

Carbon dioxide capture from the air would provide a radical alternative to currently debated options for mitigating climate change, Lackner said. He estimated that about 250,000 of the artificial trees would be needed to take care of all of the world’s carbon dioxide emissions. But time, he added, is of the essence. International accords such as the Kyoto Protocol are also key to the effort.

“We need to do it soon,” so that the carbon capturing devices could be put into use by about 2020. “The building blocks are all working now,” he said. “But we are under severe time pressure. There is enormous demand for growth in developing countries. And we are kidding ourselves if we think we can get carbon dioxide emissions to go down over the next 20 years…Sometime around 2050 we will hit a brick wall, effectively having doubled the CO2 in the atmosphere…People will be aware of that by 2020,” he predicted.

Also read: How One Mozambican Researcher Hopes to Mitigate the Climate Crisis through Coffee

With the population of urban areas expected to grow substantially in coming decades, researchers are pondering ways to plan with climate change in mind.

Published November 1, 2002

By Margaret W. Crane

In 2007, for the first time in history, the number of people living in cities will equal the number of rural dwellers, according to the most recent report of the United Nations Population Division of the Department of Economic and Social Affairs. Virtually all of the world’s anticipated population growth during the next 30 years will be concentrated in urban areas. And almost all of that growth will take place in less-developed regions.

The urbanization of early 19th-century Europe begins to look like a modest blip compared to the unplanned, unchecked growth of cities in the developing world today. Between 2000 and 2010, cities in Africa will have grown by another 100 million people, while those in Asia will have swelled by 340 million. Taken together, that’s the equivalent of adding another Hong Kong, Teheran, Chicago or Bangkok every two months.

Concerned about the coming dominance of urban areas over the world’s environment, a small but growing number of scientists have begun to focus on the city itself as simultaneous driver and subject of environmental change. In their view, the sheer quantity of people piling into cities calls for a shift of focus away from issues related to the physical environment alone and toward a more integrated approach to the broad question of urban ecology.

A New Vocabulary and Conceptual Framework

Roberta Balstad Miller, PhD, director of Columbia University’s Center for International Earth Science Information Network (CIESIN), believes scientists need a new vocabulary and a new conceptual framework to tackle the complex dialectic between physical environmental change, mushrooming cities, poverty, and rising human expectations across the globe.

“We already know a great deal about each discrete sector in the urban environmental mix,” said Miller. “Beyond atmospheres, oceans and the natural historical origins of environmental change, scientists also have investigated the interlocking issues of clean water, waste disposal, energy and land use. What we haven’t done is connect the dots that will allow us to respond to the big picture: How can cities become less vulnerable to environmental stressors? What can we learn from the environmental successes as well as the environmental problems of the great 20th-century metropolises?”

These questions form the backdrop of a new research project at the Earth Institute of Columbia University – provisionally called the Twenty-First Century Cities Project – that will examine environment and sustainable development issues in major cities worldwide. The project will focus initially on four cities: Fortaleza, Brazil; Accra, Ghana; Chennai, India; and New York, United States.

“We’re keeping New York in the mix,” said Dr. Balstad Miller, “because it affords an opportunity to study the impact of rapid urban growth over a long period of time, and also because there is so much research on the environment of New York under way at Columbia.”

Toward Sustainable Cities

The Brundtland report (Our Common Future, 1987) defined sustainable development, the theme of this summer’s Johannesburg Summit, as development that meets the needs of the present without compromising the ability to satisfy the requirements of future generations.

It’s a concept most governments agree on in principle. But with cities expanding at the rate of 10 percent per year, largely owing to massive migration fueled by poverty and conflicts in rural areas, sustainability can look like a remote ideal instead of a real-world possibility. In Johannesburg, 100 world leaders and nearly 50,000 delegates turned their energies to the challenge of bringing sustainable development back down to earth.

The Summit’s participants queried the model of urban development based on automobile-driven sprawl. They asked themselves whether it is possible for new cities laboring under a chronic shortage of resources to develop sewage and waste disposal systems in time to prevent serious outbreaks of communicable disease. They looked at the plight of unemployed urban youth and the need to find ways to cool down the social tinderbox of frustration and poverty. And they discussed the strengthening of governance – the management of society – to help smooth the expansion of cities and check chaos.

In a speech to the Megacities Foundation, British architect Lord Richard Rogers said that, above all, cities must be a vehicle for social inclusion. “This is no utopian vision,” he said. “Cities that are beautiful, safe and equitable are within our grasp.”

The Role of Sustainability

Utopian or not, the question of sustainability colors Balstad Miller’s research, and is the ultimate motivation behind the Twenty-First Century Cities Project. “Ecosystems are being bisected by highways,” she said. “Forests, wetlands and prime agricultural lands are being lost to urban development. Less land is available for indigenous animal and plant populations, whose genetic diversity is at risk. And yet we can’t halt urban growth. We need to develop sustainable approaches to a process that’s not about to go away.”

Balstad Miller, an urban historian, studies cities at three levels: The environment of the city itself, exemplified by the quality of its air, water and sanitation systems; the environment of the region, such as the city’s impact on regional weather patterns and its surrounding forested and agricultural areas; and global networks of cities as the nexus of decision-making, economic integration, and growth.

Oddly enough, she added, the real demographic story isn’t taking place in megacities like Tokyo, Mexico City, Mumbai and Sao Paulo. The number of cities with 1 million or more inhabitants grew from 80 in 1950 to more than 300 by 1990, and is projected to reach 500 by 2010. Most of the world’s urban population actually lives in the 40,000-50,000 urban centers with fewer than 1 million inhabitants, according to the United Nations Centre for Human Settlements. These urban agglomerations are a relatively new subject for those who study the complex relationship between environment and urban development. What these scientists learn may be crucial for our common future.

Also read:The Impact of Climate Change on Urban Environments

About Dr. Roberta Balstad Miller

Roberta Balstad Miller, PhD, is a senior research scientist at Columbia University and director of the University’s Center for International Earth Science Information Network (CIESIN). Dr. Miller has published extensively on science policy, information technology and scientific research, and the role of the social sciences in understanding global environmental change.

As chair of the National Research Council’s Steering Committee on Space Applications and Commercialization, she recently completed two book-length reports on public-private partnerships in remote sensing and on government use of this new technology. In addition to her many research interests, she is a published translator of the poetry of Jorge Luis Borges and N.P. van Wyck Louw. Dr. Miller was recently elected a Fellow of The New York Academy of Sciences.

New York City and the tri-state region provide a unique case study for examining the impact of climate change within the context of an urban environment.

Published November 1, 2002

By Margaret W. Crane

In Alaska the average temperature has risen by 5.4 degrees Fahrenheit over the past 30 years, and entire villages are being forced to move inland because of rising sea levels. El Niño – a disruption of the ocean-atmosphere system in the tropical Pacific – has been linked with multiple epidemics of dengue fever, malaria and cholera. Flowers in the northern hemisphere are blooming in January. Greenland’s glaciers are melting. The world’s ecosystems are in the throes of rapid transformation. And large, coastal cities are among the most vulnerable of all.

Global by definition, climate change has already begun to reshape the earth’s environment from pole to pole and from tundra to rainforest. But until recently few scientists had studied its impact on cities. Cynthia Rosenzweig, PhD, the lead author of a recent report titled Climate Change and a Global City, is among the first to look at cities – specifically New York and its environs – as distinct ecosystems that are being remodeled by global warming as relentlessly as are distant oceans, islands, forests and farmlands.

At the Forefront of Vulnerability to Climate Change

Rosenzweig and co-author William D. Solecki place global cities like New York, Sao Paulo, London and Tokyo at the forefront of vulnerability to climate change. As such, the world’s largest cities are charged with finding ways to adapt to changes that have already occurred and simultaneously reduce the greenhouse gases that are a major factor in heating up the globe in the first place.

“Global warming is on the cusp of becoming a mainstream issue,” said Rosenzweig, “an issue that’s being integrated into the day-to-day life of citizens.” This mainstreaming is emerging in tandem with a stronger-than-ever consensus among scientists that climate change has arrived and has two faces: an overall warming trend, and more frequent and severe droughts and floods. Moreover, instead of hypothesizing about global warming, researchers are now studying its effects and developing models to project the course and intensity of future changes.

To map the trajectory of projected climate change, scientists are using global climate models (GCMs), mathematical formulations of the processes – such as radiation, energy transfer by winds, cloud formation, evaporation and precipitation, and transport of heat by ocean currents – that comprise the climate system. These equations are then solved for the atmosphere, land surface, and oceans over the entire globe.

Because GCMs take into account increasing feedbacks from greenhouse gases, they project more dramatic temperature changes than do predictions based on current warming trends alone. New York’s GCM-projected temperature in the 2080s, therefore, will be from 4.4 to 10.2 degrees Fahrenheit higher. Rosenzweig and Solecki predict a more modest 2.5 F rise by the 2080s, based on current temperature trends alone minus any multiplier effect associated with greenhouse gases.

Interchange Between Scientists and Decision-Makers

The Climate Change report draws on a range of GCMs, but it also benefits from a rich interchange between scientists and decision-makers. In grappling with the complexity of the urban ecosystem, the two groups developed an innovative conceptual framework comprising three basic, intersecting elements: People, Place, and Pulse. These three P’s correspond to socio-economic conditions, physical and ecological systems, and decision-making and economic activities. “Pulse, a term we coined, is really about what makes a city a city,” said Rosenzweig. “In the past few years, I’ve gotten on familiar terms with New York’s pulse, defined roughly as the whole matrix of relationships that makes it run and hum.”

Rosenzweig’s focus on the New York region began when she was chosen to head up the Metropolitan East Coast (MEC) Regional Assessment, part of a national effort to assess the potential consequences of growing climatic instability and the engine behind the Climate Change report.

The New York metropolitan region is unique, Rosenzweig said, due to the extraordinary density and diversity of its population. Comprised of five boroughs and 26 adjacent counties in New York, New Jersey and Connecticut, it is home to a complex web of environmental problems and pressures. The area’s high demand for energy and clean water, along with its poor air quality, toxic waste dumps and threatened wetlands, are all interconnected, according to the Assessment, and call for a many-sided response.

Rising Seas Levels and Floods

For instance, New York will likely need to build higher seawalls and raise airport runways to protect against rising sea levels and increasingly severe and frequent floods. City and regional governments will be called upon to increase support for the poor and elderly, who suffer disproportionately from heat stress and respiratory ailments due to the effects of air pollution. Developers will be encouraged to disinvest from highly vulnerable coastal sites. Policymakers will need to think longer-term and learn to cooperate at the regional level. And they’ll have to get serious about reducing greenhouse gas emissions.

But it is New York’s greatest virtue – its diversity – that turns out to be its political stumbling block. The 20 million people who inhabit the area’s boroughs and neighboring counties often represent conflicting agendas. Rosenzweig believes it will take education, training and a good dose of political will to take on global warming.

In recent decades, the MEC region has experienced a marked increase in floods, droughts, heat waves, mild winters and early springs. Its annual average temperature has risen by nearly 2 degrees Fahrenheit, and precipitation levels have gone up slightly. The current rate of sea-level rise is about 0.1 inch per year, a number that is expected to increase with the further melting of glacial ice and the warming of the upper layers of the ocean. The study found that in many scenarios, the sea level is expected to rise faster than the accretion rate of wetlands, further accelerating their disappearance.

Growing Hydrologic Variability

Growing hydrologic variability is another expression of the climate change that has already begun to be felt in the region. This century, the New York area will be subject to more severe flooding during hurricanes and nor’easters. Some scientists have estimated that by the 2080s, as a worst-case scenario, a major coastal storm could occur every three to four years, compared with every 100 years in the past, while a 500-year flooding event could hit every 50 years.

It has long been the region’s default policy to place transportation and other necessary but unappealing infrastructure across and along the edges of wetlands, bays and estuaries. For example, the Hackensack Meadowlands in northern New Jersey, a low-elevation, degraded wetland, is home to an airport, port facilities, pipelines and highways. The region will need to move infrastructure inland – a matter of double urgency, Rosenzweig contends, for the sake both of the infrastructure itself and the vulnerable lands that are the first casualty of violent storms.

Climate change is, however, a bipolar phenomenon. During the summer of 1999, an intense summer drought may have contributed to the fatal outbreak of West Nile virus. More conspicuously, water conservation campaigns have become a regular feature of New York life. While the New York City water supply system – the largest in the region and one of the largest in the world – should accommodate expected hydrologic extremes, the report warns that smaller systems within the MEC region might buckle under stress. Increasingly, water distribution must be addressed intra- and inter-regionally, said Rosenzweig. Future protocols might include diverting Delaware River water from the west to reduce the impact of drought in the New York area, and vice versa.

Multiplicity of Environmental Problems

Demand for electricity also is expected to rise along with mounting temperature. No less than clean and abundant water, the area’s population requires a consistent supply of energy. But the distribution of energy continues to be far from equal. During the intense succession of heat waves over the past several summers, blackouts and brownouts plagued many of New York’s poorer neighborhoods, meaning a loss of air conditioning just when it was most critically needed.

With 27 days of temperatures above 90 degrees Fahrenheit in the summer of 1999 and 28 days over 90 degrees F (including two in September) in the summer of 2002, New Yorkers have had a recent foretaste of what’s in store. According to most climate change scenarios, the average number of days exceeding 90 degrees F (13 days in our present climate) will increase by two to three times by the 2050s.

Despite their multiplicity of environmental problems, Rosenzweig believes cities have an important role to play in shaping the earth’s future. “New York has an opportunity to rethink itself as an urban ecosystem,” she said. “For example, we can start to design buildings that are more energy-efficient. We’ll need to find ways to help people stay cooler as they adapt to a warmer environment and to reduce greenhouse gas emissions at the same time.”

The Missing Link

Although scientists haven’t yet been able to establish to an absolute certainty the causal link between human activity – especially the burning of fossil fuels – and climate change, they are largely in agreement that such change is under way. The Intergovernmental Panel on Climate Change has concluded that “there is a discernible anthropogenic signal in the climate,” and that this signal is growing. There are, however, many remaining uncertainties surrounding the rate and ultimate magnitude of the change.

By assessing its nature and extent, monitoring its trajectory, and forecasting its future impact on cities, scientists like Rosenzweig are informing a new public discussion that is just getting off the ground. But there’s no time to waste, she said: “The political and social responses to the global climate issue in cities should begin at once.”

Also read: Tales in New Urban Sustainability

About Dr. Cynthia Rosenzweig

Dr. Cynthia Rosenzweig is a research scientist at the Goddard Institute for Space Studies, where she is the leader of the Climate Impacts Group. She is an adjunct senior research scientist at the Columbia University Earth Institute and an adjunct professor at Barnard College. A recipient of a 2001 Guggenheim Fellowship, Dr. Rosenzweig led the Metropolitan East Coast Region for the U.S. National Assessment of the Potential Consequences of Climate Variability and Change.

She is a lead author of the Intergovernmental Panel on Climate Change Working Group II Third Assessment Report, and has worked on international assessments of climate change impacts, adaptation and vulnerability. Her research focuses on the impacts of environmental change, including increasing carbon dioxide, global warming, and the El Niño-Southern Oscillation, on regional, national and global scales.