Why Trees Don’t Help

While governments around the world continue to explore strategies for reducing greenhouse gas emissions, a new study suggests policymakers should focus on what needs to be achieved in the next 40 years in order to keep long-term options viable for avoiding dangerous levels of warming. The trouble is, one of the most obvious things to do is to plant more trees, but this could make things WORSE! And lawns don’t help much either.

As a result of the changing climate, treeless tundras are about to be invaded by trees. As trees move north, into climates that were formerly too cold for them, they will create warmer conditions, because the white snow and ice is being replaced by darker trees, which absorb, rather than reflect, sunlight (and this, in turn, will encourage more trees to join them). PhysOrg.com quotes Inez Fung as saying, “Alaska is already getting shrubbier. We hypothesize that there are ‘pioneers,’ like shrubs and deciduous trees, that modify the climate until it is comfortable, and then the whole clan moves in.”

PhysOrg.com quotes researcher Abigail L. Swann as saying, “Broad-leaved deciduous trees are not as dark as evergreen trees and so are generally assumed to be less important. But broad-leaved trees transpire a lot more water through their leaves and are actually able to change the water vapor content and increase the greenhouse effect. As the air warms, it can hold more water vapor, and the greenhouse effect increases further, so broad-leaved trees end up warming the entire Arctic.”

That nice green lawn isn’t good for the environment either. In fact, in certain parts of the country, total greenhouse gas emissions would actually be lower if there weren’t any lawns. It’s lawn maintenance that’s the problem: fertilizer production, mowing, leaf blowing and other lawn management practices generate greenhouse gas emissions that end up releasing 4 times the carbon they end suck up.

LiveScience.org quotes researcher Amy Townsend-Small as saying, “Lawns look great, they’re nice and green and healthy, and they’re photosynthesizing a lot of organic carbon, but the carbon-storing benefits of lawns are counteracted by fuel consumption.” Athletic fields are even worse, since they require so much emission-generating care. Due to global warming, 44 species of moths and butterflies in Central Europe have added an extra generation during the summer for the first time on record, by breeding more than once a year, meaning that in the future, we will be seeing more of these insects than we ever have before.

But these flying insects are not necessarily benign: Many of them, such as the grape berry moth, cause crop damage. In Wired.com, Susan Milius quotes population ecologist Patrick Tobin as saying, “From a pest perspective it’s an important issue.” But he says that “predicting those ripples of consequences will be “extraordinarily complex,” since additional generation of insects might lead to an increased population of the predators that feed on them and thus make life tougher for the other species these predators attack. Insects won’t be the only problem with crops in the future: Yields from some of the most important crops will begin to decline sharply when average temperatures exceed about 86 Fahrenheit. Projections are that by the end of this century much of the tropics and subtropics will regularly see growing season temperatures above that level, hotter than the hottest summers now on record.

An international panel of scientists is urging world leaders to dramatically alter their ideas about sustainable agriculture to prevent a major starvation catastrophe by the end of this century among the more than 3 billion people who live relatively close to the equator. Atmospheric scientist David Battisi says, “You’re looking at a 20 to 30% decline in production yields in the next 50 years for major crops between the latitudes of southern California or southern Europe to South Africa.

Nina Federoff, science and technology adviser to Secretary of State Hillary Rodham Clinton, says, “I grow increasingly concerned that we have not yet understood what it will take to feed a growing population on a warming planet.” The challenge is becoming more difficult because the world’s population is likely to have increased more than 30 percent, to 9 billion people, by 2050.

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