Archives—January 2012

Losing a global carbon sponge

A paper published last week in Nature reviewed a growing body of evidence that suggests that a profound loss of forest cover in the Amazaon would have worrying consequences for the rest of the planet.

In “The Amazon basin in transition“, Davidson et al. describe how the impacts of agricultural expansion and climate events such as El Niño can conspire to destroy even more forest through drought- and fire-induced deforestation. When trees die or burn, they release carbon into the atmosphere. If more trees are destroyed than grow to replace them, more carbon is released than is absorbed; the Amazon sink becomes a source. According to the article, the Amazon rainforst currently sequesters roughly 100 billion tons of carbon, an amount equivalent to the carbon release from a decade’s worth of fossil fuel use.

Currently forest cover has been reduced to about 80% of its original area; the article suggests that if forest cover approaches 40%, a critical transition from forest to savanna may occur, given feedbacks between tree cover and precipition (see our summary in Science). If this occurs, we might witness what happens with the lost of “the lungs of the planet“.


The Economics of Happiness

Green Film Series Thursday Night
“The Economics of Happiness” will be shown at 7 p.m., Thursday, Jan. 19, in G002 Hesterberg Hall in the Forestry Building. Part of the Green Film Series, the film will be followed by a discussion led by Assistant Professor Daya Muralidharan (School of Business and Economics). The series is free, but a $3 donation is requested.

Save some for the birds

In last week’s Science, a group of researchers pooled data on marine ecosystems around the world to measure the impact of fisheries on marine birds. They found that once fish and krill populations dipped below 30% of their maximum, bird populations began to suffer. Said a different way: if we want penguins, puffins, terns and kittiwakes, we’re going to have to leave them something to eat.

The study reminds me of Peter Vitousek’s famous piece (BioScience 36:368) on “Human Appropriated Net Primary Productivity” in 1986. He estimated that humans use about 40% of all of the biomass produced by plants in a given year; this claim has been supported and refuted about a dozen times since then. Postel et al. have looked at  our appropriation of water as well (estimating that we use over half of the available runoff globally). Since everything needs to eat and drink, it then becomes less surprising that we are witness to such startling losses of biodiversity (well…. perhaps we are more than just “witnessing” it!).

The difference between the “one third for the birds” study and these predecessors is policy relevance: it is probably better to know how much we can take before we do irreparable damage, than to simply know how much we are taking. Let’s see if others can follow suit with biomass, water, and land area.

Happy New Year!