Friday, 24 February 2012

Climate Change Already Harming the World's Forests

Last year I wrote about the effect that climate change has on lianas, the leafy vines that grow around trees in the tropics.  The lianas put stress on the trees, hindering the trees' growth and survival - and thus their ability to sequester carbon dioxide.  And since lianas seem better able to survive drought conditions and make use of increased carbon dioxide in the atmosphere, they form part of a dangerous feedback loop: higher greenhouse gas concentrations + warming, leading to increased liana growth leading to weakened trees leading to less carbon sequestration, leading to higher greenhouse gas concentrations.

As one of the scientists involved in the liana study noted, "All the trees will be very unhappy."

Now we're seeing that it's not just tropical trees that are in trouble.  My old grad school classmate Patrick Gonzalez recently completed a NASA-funded study that shows "significant" declines in tree density and species richness in the Sahel region of Africa. Patrick's study controlled for weather, human population, and other variables, and found that long term temperature and rainfall changes associated with climate change were by far the most important factor in explaining the loss of trees.

Thousands of miles north, scientists in Alaska and British Columbia have found 2,000 year-old yellow cedars succumbing to climate change.  These hardy trees can survive fierce storms, insects and other stresses, but require an insulating layer of snow to protect their roots from freezing soil.  The trees began dying several decades ago as the climate warmed and snow cover receded, but researchers only discovered this vulnerability after eliminating predators and fungi as potential causes and looking at physical factors.

Other evidence is anecdotal.  In January 2012, The Senator, a 38 meter (125 feet) tall pond cypress in Florida burned down.  It was the largest tree in the Eastern United States and at 3,400-3,600 years old, was one of the five oldest trees in the world.  Arson has been ruled out, but it isn't yet clear why a tree that was old when Rome was founded would suddenly catch fire.

The overall picture is that our trees are under threat.  Deforestation has long been a problem around the world, but it is increasingly clear that we are caught in a spiral of climate change and forest loss.

What can be done?

There are three ways we can help save the world's forests and enhance their contribution to ecosystem services.  All three can benefit from innovations in the carbon markets, though we shouldn't expect the carbon markets alone to solve the problem.

First, control emissions.  The majority of greenhouse gas emissions come from human activity: energy use, rice cultivation, livestock rearing.  Initiatives that reduce fossil fuel consumption and reduce methane emissions from agriculture help slow the concentration of greenhouse gas emissions in the atmosphere, and can slow the positive feedback effects that lead to global warming and tree mortality.

Second, protect the remaining forests. The Verified Carbon Standard and other organisations have pioneered mechanisms that allow the use of carbon finance to support local communities and biodiversity while protecting forests from over-harvesting, land use change and other destructive practices.

Third, plant more trees.  Around the world, community based agroforestry and afforestation projects are working to increase the area of new forest land under cultivation.  These initiatives help reduce soil erosion and enhance local incomes while sequestering carbon dioxide in a robust and verfiable manner.

Stay tuned for upcoming announcements of some of the initiatives that Carbon Clear is supporting in the effort to protect and enhance the world's forests.