Urbanization, Deforestation, Reforestation

2009 was noted as the first year that more people lived in urban spaces than in rural areas.  The hope that a majority urban population would slow the clearing of tropical forests — our most effective carbon sinks — seems, however, to have been misplaced.

The idea was simple: if more people moved into forested areas, they would naturally increase pressure on resources there.  As has been been extensively recorded, peoples of low-income in Brazil that migrated or were relocated from the city to the Amazon have traditionally engaged in slash-and-burn agriculture to clear new land for farming.  It was a logical conclusion that the migration of peoples from rural places to the city would mean that deforestation would decelerate.

But in a new study published in Nature Geoscience by scientists at Columbia’s E3B department, researchers found that deforestation is now driven largely by urbanization and trade. As lead author Ruth Defries explained: “The main drivers of tropical deforestation have shifted from small-scale landholders to domestic and international markets that are distant from the forests.”

An extensive analysis of satellite, demographic, and economic  data found strong and significant correlations between urban growth, agricultural exports, and deforestation.  The authors invoked two primary reasons: as there are fewer persons farming the land, more mechanized, or industrial, agriculture takes its place.  Additionally, as more people move to the city — where incomes and rates of consumption are generally higher — more pressure is put onto forests to produce more animal and processed food products, which require more clearing.  Some non-food agricultural items, like sugarcane or palm oil plantations grown for biofuels which are frequently geared for international markets, significantly increase pressures on forest areas, as demand for those products in developed countries grows.

The shift towards large-scale agricultural production has consequences for our climate, as forest area is reduced and greater stores of carbon released into the atmosphere.  However, that does not mean saving the forests is a lost cause, despite upward trends in urbanization.  As the paper’s abstract concludes, “efforts need to focus on reducing deforestation for industrial-scale, export-oriented agricultural production, concomitant with efforts to increase yields in non-forested lands to satisfy demands for agricultural products.”  This is not an impossible goal, and we can only hope that these suggestions are ultimately taken to heart.

Indeed, there are movements to not only slow rates of deforestation, but to regrow forests. Known as rewilding, new conservation practices that seek to reforest or otherwise return degraded ecosystems to a healthy state are springing up all over the world, according to an article by Caroline Fraser.

Expanding core park areas, establish corridors that link those core areas, and repopulating them with endemic species — like the wolf or panther — is only one aspect of rewilding. The other is integrating these areas with their local communities, and endowing preservation areas with funds that will ensure their survival in perpetuity. According to Fraser, some conservationists refer to it as “sustainable conservation.”

As the burgeoning urban population increases demand on forest areas — and Earth’s carbon sinks — it is reassuring to know that our understanding of the drivers of deforestation and climate change are growing more robust. It is also reassuring that our solutions are beginning to reflect the problems in all their complexity — that conservation of biodiversity, sequestration of carbon from the atmosphere, and the flourishing of human communities are all interrelated.

The article as published in Nature Geoscience: http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo756.html

Yale’s environment360 writeup: http://e360.yale.edu/content/digest.msp?id=2270<

Press release from the Earth Institute: http://www.earth.columbia.edu/articles/view/2635