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

The NY Times is running a cover story on how crop weeds are becoming resistant to one of the most ubiquitously used herbicides—Roundup.

This is the herbicide that farmers can spray on genetically modified crops that are resistant to its damage.  It’s widely used on major crops, such as soy, corn, canola, sugar beet, and cotton.

In theory, all weeds other than the GM crop succumb to the chemical.  As the Times story suggests, that’s not the case anymore because weeds are evolving resistance, possibly rendering Roundup and Roundup-ready GM crops ineffective.

Just as the heavy use of antibiotics contributed to the rise of drug-resistant supergerms, American farmers’ near-ubiquitous use of the weedkiller Roundup has led to the rapid growth of tenacious new superweeds.

To fight them, Mr. Anderson and farmers throughout the East, Midwest and South are being forced to spray fields with more toxic herbicides, pull weeds by hand and return to more labor-intensive methods like regular plowing.

“We’re back to where we were 20 years ago,” said Mr. Anderson, who will plow about one-third of his 3,000 acres of soybean fields this spring, more than he has in years. “We’re trying to find out what works.”

Farm experts say that such efforts could lead to higher food prices, lower crop yields, rising farm costs and more pollution of land and water.

“It is the single largest threat to production agriculture that we have ever seen,” said Andrew Wargo III, the president of the Arkansas Association of Conservation Districts.

…If frequent plowing becomes necessary again, “that is certainly a major concern for our environment,” Ken Smith, a weed scientist at the University of Arkansas, said. In addition, some critics of genetically engineered crops say that the use of extra herbicides, including some old ones that are less environmentally tolerable than Roundup, belies the claims made by the biotechnology industry that its crops would be better for the environment.

“The biotech industry is taking us into a more pesticide-dependent agriculture when they’ve always promised, and we need to be going in, the opposite direction,” said Bill Freese, a science policy analyst for the Center for Food Safety in Washington.

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Photo credit:  http://www.flickr.com/photos/kankan/ / CC BY 2.0

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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Photo Credit:

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