Biodiversity and the City 3: The consuming city

The last post focused on the surprising lack of conservation research on cities and biodiversity, given the rapid urbanization of mankind. Beyond direct habitat fragmentation, the other significant way in which cities impact biodiversity is through consumption.

The global footprint of cities is growing.

This is partly a function of sheer numbers: most people on the planet now live in urban areas. Three out of four Americans (United States) reside in cities and suburbs; two thirds of Latin American residents live in urban areas. By 2030, China will have more than 220 cities with a million or more inhabitants.

According to a Nature Conservancy study in 2008, urban growth around the world threatens biodiversity.

“While the effects of urbanization are very localized, cumulatively it is a big threat to biodiversity,” says [Robert] McDonald, the lead-author of the study. “Our urban footprint covers much of the globe and is coming closer to stomping out many endangered species and posing new risks to protected areas and parks.”

But it’s not simply population that creates the footprint.

Welcome to the Overshoot

Last Saturday was Overshoot Day (or Ecological Debt Day), which marks when the humanity’s consumption of the world’s resources surpasses the annual productive capacity of the planet. Or as RP Siegel writes:

In a way, it’s a bit like finding out on August 21st that you’re not going to get another paycheck until next New Year’s Day. How would you deal with that?

Mathis Wackernagel, the president of the Global Footprint Network, applies this concern to the state of the planet.

The situation is no less dire when it comes to our ecological budget. Climate change, biodiversity loss, deforestation, water and food shortages — these are all clear signs that we can no longer finance our consumption on credit. Nature is foreclosing.

Overshoot Day is a useful concept to explain the impact of human society. The fact that “it now takes the Earth one year and five months to regenerate what we use in a year” is pretty sobering. It’s also important to remember that the ecological debt is cumulative: the planet’s resources do not reset every year. Furthermore, the burdens created by the well-off tend to fall on more vulnerable communities elsewhere.

Finally, the rate of consumption is accelerating: this year the human footprint has reached “overshoot” a month faster than the previous year.

What drives the Overshoot?

So does population or overconsumption have the greater influence? It’s not necessarily a simple question. A couple recent items by David Biello (here) and Jonathan Foley (here) thoughtfully address the issues.

What is clear, however, is that cities have a key role in this relationship between humanity and the Earth’s resources.

Consumption driven by cities deepens the pressure on global systems. City dwellers tend to have higher incomes (and greater income disparities) and inhabit new social relationships. This combination fosters new markets and encourages consumerism — a kind of hyper-consumption stoked by advertising.

Supply chains radiate like tentacles from urban areas (themselves sprawling) to the farthest reaches of the planet. Food mile calculations start in distant landscapes and terminate in urban supermarkets and restaurants.

While large cities are notably energy efficient, the gains of urban density can be quickly outweighed by the increase in total embodied energy of goods consumed. According to the UN Environmental Program (UNEP),

One third of the average US household’s carbon footprint is due to emissions caused abroad producing goods imported into the US market.

Urban dwellers in the US, Canada, Australia, and other developed nations have a much larger footprint that city folk in other countries. Wackernagel and William Rees estimate that

a typical North American city with a population of 650,000 would require 30,000 square kilometres of land—an area roughly the size of Vancouver Island, Canada—to meet domestic needs alone without even including the environmental demands of industry. In comparison, a similar size city in India would require 2,800 square kilometres.

The UNEP study suggested that agriculture and energy are the primary forces of environmental change.

“How the world is fed and fueled will in large part define development in the 21st century as one that is increasingly sustainable or a dead end for billions of people.

“Current patterns of production and consumption of both fossil fuels and food are draining freshwater supplies; triggering losses of economically-important ecosystems such as forests; intensifying disease and death rates and raising levels of pollution to unsustainable levels.

And it is an urban penchant for consumption that continues to drive resource extraction, manufacturing, and their related impacts around the globe.

A recent study (also here) found that the primary forces driving deforestation are the rise of big cities and international trade. Increasing urban demand for agricultural products and biofuels greatly impact land use.

“The main drivers of tropical deforestation have shifted from small-scale landholders to domestic and international markets that are distant from the forests,” said lead author Ruth DeFries, a professor at the Earth Institute’s Center for Environmental Research and Conservation. “One line of thinking was that concentrating people in cities would leave a lot more room for nature. But those people in cities and the rest of the world need to be fed. That creates a demand for industrial-scale clearing.”

This vast shift is now happening primarily in the global South.

But the demand itself is not solely from developed nations. While cities in the developed world have a larger footprint, this pattern is being mirrored in the developing world, as more people funnel into urban areas. The food demands of cities in the emerging economies of the BRIC nations (Brazil, Russia, India, and China), in particular, will push agricultural expansion.

Agricultural output in the Bric nations will grow three times as fast as in the major developed countries, the joint United Nations-OECD study said.

And rising incomes and urbanisation in developing states will drive growth.

“Developing countries will provide the main source of growth for world agricultural production, consumption and trade,” the report said.

“As incomes rise, diets are expected to slowly diversify away from staple foods towards increased meats and processed foods that will favour livestock and dairy products.

“For virtually all commodities, the projected growth in imports and exports of developing economies [over the next decade] exceeds that of the OECD area,” said the report.

The vast demand encourages agribusiness-driven exploitation. Where the main causes of deforestation were once the cumulative impacts of individual actions, now large-scale land grabs and conversion to agriculture have become a primary concern. Opportunistic agribusiness tends to exploit nations with weak governance structures. So this is not simply an issue of urban-driven demand, but also one of land tenure in the Global South, distribution, and a global food system.

Not just mega-cities

It’s uncertain (at least to me) whether the hyperconsuming mega-cities or the small to medium-sized cities — where most of global population growth during the next few decades will occur — will have a greater collective footprint.

The carbon footprint — and impact on land use and deforestation — of the megacities may be larger given the consumption levels. The sheer number and distribution of smaller cities, however, may end up disrupting more habitat and contributing more to biodiversity loss.

The rapid expansion of cities will test the capacity of urban governance (i.e., haphazard systems, untrained managers, corruption).  Small to medium-sized cities may face the “double whammy” of rapid, unplanned expansion and a “brain drain” of more talented or educated individuals to larger cities. The urban response will determine the scale of social and environmental impacts.

In any case, the future of humanity will be found in cities. As Robert McDonald from the Nature Conservancy concludes:

“Only by addressing this growing conflict between cities and biodiversity can society achieve genuine conservation in an urbanizing world.”

On Dust

This is the Amazon rainforest. Or at least a part of it.

Last week, an item in the Guardian (UK) highlighted a surprising connection between the Amazon rainforest and the Sahara desert — how one region in Chad supplies the Amazon with half of the rainforest’s mineral nutrients.

Around 40m tons of dust is carried by prevailing winds from the Sahara to fertilise the Amazon basin each year. This is a very satisfying finding, since the extraordinary fertility of the Amazon rainforest – one of the richest and most biodiverse places on earth – has been a puzzle. Tropical rains leach nutrients from jungle soils, and the soils of the Amazon forest are notoriously poor, which is why clearance for cattle farming is such a bad idea. Biologists had calculated that the forest needed at least 50m tons of fresh mineral nutrient each year to keep its trees tall and in leaf. In 2006 an international team of researchers established that at least half of this annual mineral supply is quarried from one tiny location in the Sahara, the Bodélé depression in Chad. A combination of fortuitously placed mountain ranges that flank a basin of diatomite sands so focus the winter winds as to scour the depression and lift from it an average of 700,000 tons of dust each day, and air-freight it across the Atlantic.

So for thousands of years, and without any fuss, a tiny part of one of Africa’s poorest countries has annually subsidised the growth economy of one of the world’s most richly endowed. This discovery is yet another insight into the intricate dance performed by earth, air, fire and water in the service of life; and another reminder of the enduring intercontinental interdependence that sustains human civilisation. We should respect the IUCN‘s [International Union for Conservation of Nature] concern for the deserts. Without green things, we could not breathe. Without deserts, there might be no forests.

NASA’s Earth Observatory posts satellite images of massive dust clouds — including the one above — blowing from deserts (and other brilliant photographs from space).

According to the Climate Matters blog of Columbia University’s Earth Institute, scientists from a wide range of disciplines convened earlier this summer to coordinate their research on dust, much in the way that the oceanographic community came together in the 1990s to collaborate more effectively. Why dust?

Dust is a global phenomenon. Where it comes from, where it goes, and how it impacts climate and the biogeochemistry of land and oceans are questions that span all the realms of earth science.


Dust influences the radiative balance of the planet in two different ways, either directly by scattering and absorbing incoming solar radiation, or indirectly by changing the optical properties of clouds, themselves an important player in the climate system. Dust also contains iron, a limiting nutrient in many areas of the ocean, so when dust falls onto the ocean, it can act as a fertilizer for the growth of algae, or phytoplankton, which uses CO2. Dust not only affects climate, but also is influenced by it: its production, atmospheric transport and deposition are sensitive to climatic conditions.

During Earth’s history, dust has been strongly linked with climatic conditions: Ice cores and marine sediments tell us that the ice age world was much dustier than today’s world. Thus dust is both a driver and a passive recorder of climate change under different climatic regimes of the Earth’s past. However, its exact role in past climate change remains poorly constrained. Understanding the links between dust and climate in the past will be crucial to evaluate the future impacts of dust on the Earth’s climate system in a warming world.

One could add a recent study (here and here) that suggests soot may be the second greatest contributor to global warming — behind carbon dioxide, but ahead of methane. Produced by the combustion of fossil fuels and borne around the globe by winds, soot helps to accelerate the melting of glaciers and Arctic ice by absorbing more of the sun’s radiation. Controlling soot may be the most effective short-term measure to slow warming.

On this ceaseless swirl of land, air, and water, everything is in motion. The movement patterns are part of the relative stability of the climate system around which life has evolved and upon which we rely. Climate change’s uncertain impacts on the atmospheric and oceanic flow and upon the well-timed relationships between plants and animals naturally raise great concern. Wind and water also transport pollutants across state and national boundaries and even from continent to continent. Whether they involve global warming or specific pollutants, these vast connections make all life “downstream.”

Biodiversity and the City 2: In an urban world, where are the ecologists?

What happens to biodiversity in areas that become more urban? The short answer, not surprisingly, is that urbanization decreases biodiversity.

In a review article published in Science a couple years ago, Nancy Grimm and colleagues wrote that urban land use tends to

reduce both species richness and evenness for most biotic communities, despite increases in abundance and biomass of birds and arthropods. Because the urban footprint extends far beyond municipal boundaries, urbanization may also reduce native species diversity at regional and global scales.

Cities have a huge impact through local habitat loss and fragmentation. More broadly, urban consumption helps to drive global environmental change.

The longer answer, however, is that we don’t know enough about urban biodiversity and how to protect ecological systems amidst urban growth.

This is significant, because the Earth is more and more an urban planet. The Population Institute recently forecast that the human population will grow to nearly 9.5 billion by 2050. Between natural increase and migration, most of the population growth will occur in cities in developing nations. By 2030, two thirds of humans will live in urban areas.

Climate change/destabilization, biodiversity loss, and agricultural land grabs (stemming in part from food demand from urban areas) may drive much of the urban migration in the developing world.

“Ecologists shun the urban jungle”

While tools like wildlife corridors and habitat conservation plans can help to preserve ecosystems facing rapid urban growth, several recent items highlight the vast challenge of supporting biodiversity in an urbanizing world.

First, conservation research is simply not looking at urban areas.

An item in Nature News suggests that only one in six papers on conservation addressed regions used by humans and only 4% studied urban or suburban areas.

The world’s top ecologists are failing to study the landscapes that most need work, and they risk delaying conservation efforts and making their subject irrelevant.

That is the stark message from US researchers who have quantified the extent to which ecologists devote themselves to pristine wilderness at the expense of inhabited regions. The bias is a major problem for both the field and the environment, they say, because it is areas used by humans — which take up most of the Earth’s land-mass — that are in most need of conservation.

The piece discusses work presented this past week at the annual meeting of the Ecological Society of America (ESA). According to Terry Chapin, the new president of the ESA:

It is really important that ecologists do research on areas populated by people. I would hate to go so far as to say studies of pristine areas are not important, but we clearly need to know much more about the direct ways in which we are affecting the biosphere.

There are undoubtedly ecologists whose research focuses on the urban landscape, but this still appears to be an emerging field of study. This article mentions five research “nodes” addressing urban environments as social-ecological systems (including the previously quoted Nancy Grimm):

Marina Alberti’s at the University of Washington, Nancy Grimm at Arizona State University, Stewart Pickett and colleagues at the Cary Institute of Ecosystem Studies in New York, Mark McDonnell at the Australian Research Center for Urban Ecology, and Herbert Sukopp in Germany.

Second, as a post on Conservation Bytes suggests, conservation studies rarely lead to actual conservation, in part because of the siloed approach of researchers whose communication primarily echoes within the academic arena. The presentation cited was specific to tropical forest research, but the post also discussed considerations for all researchers.

These tidbits reflect the recent state of biodiversity research, which may in turn highlight the traditional bent of academia and its funding sources, as well as the difficulties of studying complex urban-ecosystem interactions. They also say little about the efforts of ecologists working for nonprofit organizations, such as Conservation International or the Nature Conservancy or especially local conservation groups, or for local or state departments of natural resources/environment/parks.

But the two realizations above may contribute to a significant third item: While there has been an increase in the number of protected areas around the globe, little progress has been made towards the goals set by the Convention on Biological Diversity (2002).

On a positive note, 2010 and the International Year of Biodiversity have brought relative successes on the biodiversity front, even as climate change’s roller coaster year continues (Copenhagen, Climategate, climate bill in the US Congress, etc.). The Economics of Ecosystems and Biodiversity (TEEB) study brought attention to the economic benefits of biodiversity and ecosystem services. A June conference in Busan, Korea, has led to the creation of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) — basically an IPCC for biodiversity. IPBES promises to bring greater coherence to fragmented conservation efforts.

Given the growing human impact on living systems across the globe, more foresight, research, and action is needed to ensure that governments (and individuals) protect urbanizing landscapes for biodiversity as well as climate change resilience.

Part I focused on a wonderful video promoting the Biodiversity Campaign from the European Commission on the Environment.

Biodiversity and the City

Part I

On Worldchanging, Amanda Reed posted this remarkable video from the Biodiversity Campaign that the European Commission on the Environment launched earlier this year.

It’s a lovely piece that I hope reaches a large audience. What is surprising is the explicit focus on connecting urbanization and biodiversity loss. The ad seeks to shift the ways in which city dwellers envision the world.

This is brilliant. Now that more than four billion human beings — half of the human population — live in urban settlements, fostering a deeper understanding of connections between humans and nature and our intertwined futures has become increasingly difficult. Yet this remains a central challenge for our civilization, as it continues to press alarmingly against planetary boundaries.

According to the description of the video:

Biodiversity is the variety of life on earth including ecosystems, species and genes. We are part of biodiversity and our lives depend on it. And this life supporting biodiversity is disappearing from our cities at an alarming rate. Today it is the sparrow, but tomorrow it could be us.

Amanda Reed writes in the Worldchanging article:

While the video above is more about a problem than a solution, I think it is a compelling way to communicate the issue of biodiversity and interconnectedness to a large audience, which in turn can perhaps spur greater action and interest in solutions. The trick though, is to grasp the large scope of the issue, and spur action at the right scale and speed.

Reed goes on to suggest that the actions for change recommended by the Biodiversity Campaign are overly limited to the individual scale and, hence, insufficient to address the “large-scale systems of industry” that drive global biodiversity loss. Indeed, the problems are in large part systemic, making change necessary at many levels.

Business decisions make sense from a narrowly economic perspective optimizing the path from source to market. New reports connecting business and biodiversity — such as The Economics of Ecosystems and Biodiversity (TEEB) — will help to educate the business community and policy makers, expand consideration of ecosystem services, and tip businesses towards less harmful options.

Campaigns that reframe our relationship with nature – specifically as an urban species – serve as an important complement.