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.”