The silver bullet solution to climate change in many people's book is to simply 'plant a tree'. A recent study indicates that it might not be quite that simple...
The ability of forests to soak up man-made carbon dioxide is weakening, according to an analysis of two decades of data from more than 30 sites in the frozen north.The finding published today is crucial, because it means that more of the CO2 we release will end up affecting the climate in the atmosphere rather than being safely locked away in trees or soil.
The results may partly explain recent studies suggesting that the amount of CO2 in the atmosphere is increasing faster than expected. If higher temperatures mean less carbon is soaked up by plants and microbes, global warming will accelerate.
... The surprise rethink concerns abundant evidence from around the world that winter is starting later and spring earlier. In northern latitudes, spring and autumn temperatures have risen by 1.1C and 0.8C respectively in the past two decades. That means a longer growing season for plants, which scientists thought should be a good thing for slowing warming....If the report is correct, this is a major additional feedback loop that has the potential to greatly accelerate climate change.The team focused particularly on the date in autumn at which the forests switched from being a net sink for carbon into a net source. Instead of moving later in the year as they had expected, this date actually got earlier - in some places by a few days, but in others by a few weeks. -- Guardian
The most obvious solution in the battle against global warming, of course, is to significantly reduce the amount of fossil fuels getting pulled out of the ground and burnt (i.e. reduce greenhouse gas inputs into the atmosphere). Another is to utilise more powerful carbon sinks (i.e. increase greenhouse gas extraction from the atmosphere). There is one change we can make in our way of working that would accomplish both! Although trees might not be keeping up, there are still armies of plants and organisms waiting to lend a hand -- if only we'd utilise them. I'm referring, in particular, to moving towards more sustainable agriculture.
Twenty-three years of ongoing research at The Rodale Institute Experimental Farm already provides strong evidence that organic farming helps combat global warming by capturing atmospheric carbon dioxide and incorporating it into the soil, whereas conventional farming exacerbates the greenhouse effect by producing a net release of carbon into the atmosphere.The key lies in the handling of organic matter (OM): because soil organic matter is primarily carbon, increases in soil OM levels will be directly correlated with carbon sequestration. While conventional farming typically depletes soil OM, organic farming builds it through the use of composted animal manures and cover crops. -- New Farm
The world's soils are the earth's second largest carbon sink (next to the oceans). As we've shared before, proper soil management is a powerful and highly effective method of removing carbon from the atmosphere, as well as reducing fossil fuel use, reducing toxic chemical use and runoff, improving plant (and thus human) health, and more (actually, a lot more if we also simultaneously incentivise the relocalisation of our markets).
- Converting the U.S.'s 160 million corn and soybean acres to organic production would sequester enough carbon to satisfy 73 percent of the Kyoto targets for CO2 reduction in the U.S.
- U.S. agriculture as currently practiced emits a total of 1.5 trillion pounds of CO2 annually into the atmosphere. Converting all U.S. cropland to organic would not only wipe out agriculture's massive emission problem. By eliminating energy-costly chemical fertilizers, it would actually give us a net increase in soil carbon of 734 billion pounds. - Portland Independent Media Center
An old post, but I am tempted to reply as the result of the study is hardly crucial. The study concentrates on northern trees that go dormant during the winter time; thus, their intrinsic capacity to absorb atmospheric CO2 is not as great as the trees in warmer climates that do not go dormant. Furthermore, the timing at which trees go dormant is often determined by the internal mechanism of the trees themselves, not by external temperature variance which is less reliable trigger--at least from the perspective of trees--than the internal one, or the variance in light which is more precisely regulated by seasonal change in Earth's orbit around the sun and the radiation output level of the sun itself.
Thus the study's assumption that having a few extra warmer days in the northern taigas should keep trees growing longer is not tenable. The reason northern trees are becoming dormant earlier probably has something to do with a slight decrease in the solar radiation output of the past 10 years or so--an insignificant amount by human standards, but perhaps not by trees' standards.
Furthermore, there is no such thing as "trees giving up CO2 battle," as they are always looking for more food, and CO2 is their food. The water they absorb is mostly used to help the respiration and absorption process in incorporating atmospheric CO2. Once sufficient amount of CO2 has been absorbed into trees though their stomata, stomata close, thus preventing further water loss due to evaporation. In other words, in a CO2 rich atmosphere, plants actually use less amount of water--a counterintuitive but experimental fact. Stomata have to stay open in a CO2 poor atmosphere longer, thus slowing down the carbon absorption cycle of trees and, consequently, their growth rate.
Much of the "battle loss" suffered by Earth's trees is due to the massive scale of deforestation that has been steadily escalating since the mid-twentieth century--vast majority of which has occurred in the warmer evergreen tree growing regions of Earth. To be fair, northern trees do give up the "CO2 battle," but only during their dormancy, not when they are fully "awake." Overall, however, they are not as prolific a CO2 eater as their relatives in the warmer climate; hence counting on them to do more work is a misplaced hope, unless, of course, we plant more trees in the taigas.
Written in May 2009