Saturday, September 20, 2014

Trees are bad for the environment

Considering all the interactions, large-scale increases in forest cover can actually make global warming worse. ...

The dark color of trees means that they absorb more of the sun’s energy and raise the planet’s surface temperature.

Climate scientists have calculated the effect of increasing forest cover on surface temperature. Their conclusion is that planting trees in the tropics would lead to cooling, but in colder regions, it would cause warming. ...

...we can’t reliably predict whether large-scale forestation would help to control the earth’s rising temperatures.

Worse, trees emit reactive volatile gases that contribute to air pollution and are hazardous to human health. These emissions are crucial to trees — to protect themselves from environmental stresses like sweltering heat and bug infestations. In summer, the eastern United States is the world’s major hot spot for volatile organic compounds (V.O.C.s) from trees.

As these compounds mix with fossil-fuel pollution from cars and industry, an even more harmful cocktail of airborne toxic chemicals is created. ...

Chemical reactions involving tree V.O.C.s produce methane and ozone, two powerful greenhouse gases, and form particles that can affect the condensation of clouds. Research by my group at the Yale School of Forestry and Environmental Studies, and by other laboratories, suggests that changes in tree V.O.C.s affect the climate on a scale similar to changes in the earth’s surface color and carbon storage capacity.

While trees provide carbon storage, forestry is not a permanent solution because trees and soil also “breathe” — that is, burn oxygen and release carbon dioxide back into the air. Eventually, all of the carbon finds its way back into the atmosphere when trees die or burn.

Moreover, it is a myth that photosynthesis controls the amount of oxygen in the atmosphere. Even if all photosynthesis on the planet were shut down, the atmosphere’s oxygen content would change by less than 1 percent.