Archive for the ‘population’ Category
|New land for agriculture coming mainly at the expense of tropical ecosystems
Wednesday, September 1st, 2010
There have traditionally been two ways to produce more food for an increasing population: Convert native ecosystems like forests and grasslands to agricultural fields (what we call “extensification”) or make the yields on existing croplands go up, through the use of things like machinery, fertilizers, irrigation, pesticides, and GMOs (what we call “intensification”).
Historically, these processes have occurred in tandem: an initial phase of extensification and land clearing followed by development and intensification. Converting North America’s prairies to corn and wheat in the 19th century is a classic example of the former, whereas 20th-century rise of fossil fuels, and the machines and fertilizer they support, is an example of the latter.
So while it’s not surprising to learn that developing nations in tropical regions are experiencing significant deforestation for food production, as Holly Gibbs and colleagues at Stanford describe in the early edition of the Proceedings of the National Academy of Sciences (citations removed for clarity), it’s important to understand the magnitude of ecosystem change as well as the drivers of change:
This study confirms that rainforests were the primary source for new agricultural land throughout the tropics during the 1980s and 1990s. More than 80% of new agricultural land came from intact and disturbed forests. Although differences occur across the tropical forest belt, the basic pattern is the same: The majority of the land for agricultural and tree plantation expansion comes from forests, woodlands, and savannas, not from previously cleared lands.
Worldwide demand for agricultural products is expected to increase by ∼50% by 2050, and evidence suggests that tropical countries will be called on to meet much of this demand. Consider, for example, that in developed countries the agricultural land area,
including pastures and permanent croplands, decreased by more than 412 million ha (34%) between 1995 and 2007, whereas developing countries saw increases of nearly 400 million ha (17.1%). Moreover, developing countries expanded their permanent croplands by 10.1% during the current decade alone, while permanent cropland areas in developed countries remained generally stable. If the agricultural expansion trends documented here for 1980–2000 persist, we can expect major clearing of intact and disturbed forest to continue and increase across the tropics to help meet swelling demands for food, fodder, and fuel.
Indeed, recent studies confirm that large-scale agro-industrial expansion is the dominant driver of deforestation in this decade, showing that forests fall as commodity markets boom. Rising commodity prices have been implicated in the destruction of Amazonian rainforests for soy production and peat swamp forests for oil palm production in Southeast Asia. Drivers of cropland expansion may impact forests directly through local or regional demand or indirectly through more globalized demand that may occur via market-mediated effects. Although this study does not specifically assess displacement or indirect land use changes, it does highlight the likelihood that intact and degraded forests will be replaced by agricultural land when such changes occur. Regardless of the mechanism, concern continues to mount about the large emissions of carbon dioxide that result when tropical forests are felled and often burned to make room for new agricultural land.
This was more of a land use change analysis, so it didn’t include a lot on the global drivers causing deforestation. It would be a mistake, for instance, to ascribe all of this change to population growth in these tropical regions or efforts to supply more food to people living there. Rather, extensification today is a global phenomenon driven by international trade, as the developing world loses native ecosystems to feed other countries. And destroying forests and peatlands is a major net source of greenhouse gas emissions, so we’re also warming climate as an unintended consequence.
Why not just halt extensification and switch to intensification on existing farmland? It’s expensive—moreso than simply clearing more land in many cases. When the demand for cheap food rules the world, forest clearing in poor countries with abundant, cheap land is often what you get.
It should make us all pause considering that the environmental effects of the demand for goods like soy and palm oil by the industrialized world are being externalized to tropical countries. We are now chopping down tropical forests to make soy burgers, biodiesel, and snack foods. As Cameron Scott notes, “The Amazon, It’s What’s for Dinner.”
Reference:
H. K. Gibbs, A. S. Ruesch, F. Achard, M. K. Clayton, P. Holmgrene, N. Ramankutty, and J. A. Foley (2010). Tropical forests were the primary sources of new agricultural land in the 1980s and 1990s Proceedings of the National Academy of Sciences
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Photo courtesy of leoffreitas
Posted in biodiversity science, biofuels, food and agriculture, land use, population | No Comments »
City dwellers of the future: Urban heat island warming may be as large as doubling CO2
Monday, April 19th, 2010
I remember driving on a freeway in Phoenix after midnight in 1990. The temperature was a cool 102 degrees F after breaking the all-time heat record of 126 F that day. Deserts are good at cooling off at night. But with all of the built environment in Phoenix storing heat from the day, the sidewalks, roads, and even swimming pools felt like they were being heated.
We all have probably experienced urban heat islands—the mass of dark asphalt and concrete absorbing solar radiation and radiating it back to space as heat. The lack of water exacerbates the situation because there is little-to-no evaporative cooling. Waste heat from cars, machines, air conditioners, and even human bodies also heat up the air. And the warmer it gets, the stronger the tendency to crank up the air conditioners, generating even more waste heat.
The problem is potentially large in areas like the Middle East, India, parts of Africa, and the American Southwest, where rapid urbanization in warm, dry environments has the potential to make some urban areas much warmer at night than surrounding rural areas.
In a forthcoming article in Geophysical Research Letters1, Mark McCarthy and colleagues at the Met Office, Hadley Centre, UK used a climate model that examines what climate might look like in a doubled CO2 world and calculates the added warming caused by urbanization and wasted heat.
Their results were eye-opening:
- Urban regions in places like the Arabian Peninsula, Iran, and India may experience night time warming by as much as 3-5 degrees C above and beyond that caused by doubled CO2 alone.
- The number of hot nights per year (defined as temperatures in the 99th percentile of nonurban areas) increase in the following cities:
- London: 1-2 hot nights now vs. up to 10 hot nights in 2050
- Sydney: 1-2 hot nights now vs. up to 15 hot nights in 2050
- Delhi: 5-10 hot nights now vs. up to 30 hot nights in 2050
- Beijing: 3-6 hot nights now vs. up to 50 hot nights in 2050
- Los Angeles: 8-12 hot nights now vs. up to 40 hot nights in 2050
- Tehran: 20 hot nights now vs. up to 60 hot nights in 2050
- Sao Paulo: <5 hot nights now vs. up to 80 hot nights in 2050
- Lagos (Nigeria): <5 hot nights now vs. up to 150 hot nights in 2050
As mentioned in an earlier post, we only need to remember Chicago in 1995 to recall the deadly impact that heat waves can have on urban people. And as we saw in that unfortunate example, the victims were disproportionately the elderly and African American.
Although we may not be able to mitigate this warming, basic adaptation steps should be set into motion, including re-thinking urban design, making cities more resilient to hot environments, developing better energy and technology solutions (including cooling), installing green roofs, and putting into place emergency disaster plans and social safety nets for vulnerable populations.
1Mark McCarthy, Martin Best, and Richard Betts (2010). Climate change in cities due to global warming and urban effects Geophysical Research Letters : 10.1029/2010GL042845
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Posted in climate adaptation, climate change science, energy, environmental justice, health, land use, population, race and class, sustainability, technology, urban | 3 Comments »
Land consumption and open space loss across U.S. cities
Tuesday, March 2nd, 2010
The issue of land use change is a complex, with many factors being important historically, such as
- population growth (more land required for more people)
- technology (e.g., automobiles made suburban expansion feasible)
- economics (cheaper land and rents in suburbs compared to cities)
- policy (things like 30-yr mortgages, mortgage insurance, and FHA loans had a large impact on urban sprawl because they often made it cheaper to own rather than rent)
- cultural values (the romanticized notion of a detached home in a safe, pollution-free neighborhood with good schools)
In this week’s PLoS One, Robert McDonald and colleagues1 examined land use change for 274 metro areas (figure 1) in the U.S. to determine tends across cities.
Their results were interesting (excerpts):
- 1.4 million ha of open space was lost, and the amount lost in a given city was correlated with population growth.
- American cities vary by more than an order of magnitude in their MSA-wide per capita land consumption. Generally large cities have small per capita land consumption, with the five smallest in 2000 being New York (459 m2/person), Miami (476 m2/person), Philadelphia (519 m2/person), Los Angeles (535 m2/person), and Washington, DC (536 m2/person). Conversely, many small cities have large per capita land consumption, with the five biggest in 2000 being Grand Forks, ND (5394 m2/person), Bismark, ND (3913 m2/person), Flagstaff, AZ (3381 m2/person), Enid, OK (3249 m2/person), and Cheyenne, WY (3073 m2/person).
- The per capita land consumption (m2/person) of most cities decreased on average over the decade from 1,564 to 1,454 m 2/person, but there was substantial regional variation and some cities even increased.
- Cities with greater conservation funding or more reform-minded zoning tended to decrease in per capita land consumption (scroll to table 1) more than other cities.
- The inequality of land consumption varied geographically, with less inequality on the East Coast compared to the West Coast (scroll to figure 4).
They provide a simplified snapshot of how development changes with history and geography (for a more-thorough yet readable treatment of land use in the U.S., check out Crabgrass Frontier by Kenneth Jackson):
The process of development plays out differently in cities with different socioeconomic histories. Moreover, cultural differences exist among and within many U.S. cities, leading to varying spatial patterns of development. However, a general historical pattern exists. In many U.S. cities, an urban core existed in the decades or centuries prior to the widespread use of the automobile, and these neighborhoods have high population density and small amounts of developed area per capita. The surrounding suburban and exurban areas, created predominately after WWII, contain residents living at lower population density and consume more land per capita. There are substantial economic links between these two zones, and in contemporary U.S. cities commuting occurs in both directions. Northeast U.S. cities that developed before the automobile typically follow this narrative. Many have a relatively dense urban core, but have adopted zoning policies that ensure contemporary suburban settlements occur at lower density. While they remain dense compared to other U.S. cities, they are getting less dense over time, as proportionally more of the population is in suburban areas. The declining manufacturing cities of the Rust Belt and the Southern Appalachians are an extreme example of this spreading out of population.
Southeastern U.S. cities, excluding Florida, are often newer and have less of a legacy of a dense urban core. They do not appear to be getting markedly denser, and the relatively fast population growth of these cities implies that their total impact on natural habitat in coming decades will be large. In contrast to the Southeast, Western cities appear to be getting denser, including those that do not have a historical legacy of a dense urban core such as Phoenix. These Western cities are often still growing quickly and consuming a great deal of land, but contemporary development is making these cities denser than they were previously. Many of these Western cities have a strong conservation culture, and the degree of conservation funding and reform-minded zoning correlates with how much denser they are getting. However, it should be noted that contemporary development in Western cities is still well below the densities found in the dense urban core of Northeastern U.S. cities, posing problems for designing effective public transit systems.
1McDonald, R., Forman, R., & Kareiva, P. (2010). Open Space Loss and Land Inequality in United States’ Cities, 1990–2000 PLoS ONE, 5 (3) DOI: 10.1371/journal.pone.0009509
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Photo Credit: http://www.flickr.com/photos/bobjagendorf/ / CC BY-NC 2.0
Posted in behavior, land use, nature and culture, policy, population, sustainability, transportation, urban | 1 Comment »
Science Magazine considers whether decreasing meat consumption can increase global food security
Saturday, February 13th, 2010
In this week’s special issue devoted to food security, Science asks what it will take to feed 9 billion people by mid century.
Food insecurity—the inability of people to feed themselves—may rise if food supply cannot keep pace with population. This is a concern that goes back over 200 years to Thomas Malthus.
One theme shows up in a few articles: Can reducing meat consumption help in the battle to feed more people?
Erik Stokstad’s news feature (subscription required)1 provides a nice lead:
The United States, for instance, has just 4.5% of the world’s population but accounts for about 15% of global meat consumption. Americans consume about 330 grams of meat a day on average—the equivalent of three quarter-pound hamburgers. In contrast, the U.S. Department of Agriculture recommends that most people consume just 142 to 184 grams of meat and beans daily. In the developing world, daily meat consumption averages just 80 grams. Those numbers suggest that people living in the United States and other wealthy nations could increase world grain supplies simply by forgoing that extra burger or chop.
However, he interviews researchers and cites studies that raise a number of issues potentially complicating this story…
Tags: meat and diet
Posted in behavior, food and agriculture, population, solutions | 1 Comment »
Haiti’s story
Wednesday, January 13th, 2010
Little good news is coming out of Haiti these days. There’s a deep social-environmental history that needs to be explored to understand why crises like poverty, AIDS, mudslides, and this week’s earthquake have been so devastating to the Haitian people.
I have written a bit about this history for one of the book projects I’m working on. Below are a few excerpts, but before reading further, please consider helping with the humanitarian relief for earthquake victims:
- Doctors Without Borders USA
- AmeriCares
- An additional list of aid agencies can be found at the NY Times.
Tags: Haiti
Posted in conflict, energy, food and agriculture, health, nature and culture, population, race and class, risk analysis, social science | 2 Comments »
Thoughts on addressing population and climate change in a just and ethical manner
Tuesday, January 12th, 2010
That’s the title of a new article1 by Suzanne Petroni in the latest issue of Population and Environment (subscription required). She begins by acknowledging the complex history between these issues:
There is, in the field of population and reproductive health, a present debate around the merits and deficiencies of bringing the issue of global population growth back to the public agenda. Many see the current attention to the issue of climate change as an opening in which to make the case that global warming can not be alleviated or reversed without slowing population growth. They believe that linking population growth and climate change will help governments to see the exigency of the matter, and will place family planning back into the political realm as an urgent matter of national and environmental security….
But others worry that focusing on the environmental impacts of demographic change places at risk the hard-fought and long-developed global consensus that individual rights and empowerment are what matters most in fostering just and sustainable development. They fear that a renewed focus on the impacts of the growth of our global population poses a risk of drawing the international community back to numbers-driven policies and programs, which have not always prioritized individual interests…
- [D]oes the right of the community to live on a healthy planet trump the right of the individual to decide for him or herself, without external pressure, their own desired level of fertility?
- Does the United States, which emits a hugely disproportionate amount of greenhouse gases, have a right to suggest that other countries reduce their rates of population growth in order to somehow compensate for our profligate and consumptive lifestyles?
- How can we best balance a duty to future generations with the values of individual freedom and equality among the planet’s current occupants?
- And, while coercive means of population control have been widely condemned in most parts of the world, does making the ‘‘population-climate change connection’’ run the risk of countries seeing population control as an ‘‘easy fix’’ to the environmental challenges we face?
In light of these huge questions, what are her recommendations?
Posted in behavior, gender, health, population | No Comments »
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