01 CONJECTURE
C02 and trees: boon or bane?
So CO2 is released into the atmosphere causing global warming, right? Um, maybe. But CO2 is quite important for trees right? I guess so. So what is the fuss about..? If trees need CO2 to grow, why not simply increase our CO2 emissions so more trees can grow and spread their seeds across the world? We would not even need tree planting initiatives if we just did that, right? Well it’s a tad more complex than that.
A shaky equilibrium
Yes, we are coming out of a little ice age (14th-19th century). Yes, there is a rise in carbon dioxide and global temperatures. Whether technologically advanced human civs are the cause (or a contributing factor) of this or not, is not the focal point of this article – it is not? – nor are the positive or negative effects of this evolution, but rather the fragile relationship between trees and carbon dioxide.
1. Carbon sinks
Forests – and thus trees in general – are often thought of as terrestrial carbon sinks: photosynthesis allows trees to turn carbon dioxide absorbed from the atmosphere into various carbon-based sugars they need to function and grow. Some studies estimate that trees take in about 30% of carbon emissions worldwide, which is great news for anyone concerned about carbon dioxide. In fact, trees hold on to carbon dioxide in every part of its anatomy (trunk, branches, leaves and roots). So far so great.
2. Carbon emitters
Yes, but.., That is not where the story ends. Carbon dioxide stored by trees is released when they meet their end or are set ablaze by fire. Moreover, trees release part of the carbon dioxide they absorb back into the atmosphere via respiration or into the soil as they decompose.
3. Too much carbon dioxide
Now here is the kicker. Studies show that trees grow faster the more carbon dioxide they consume, but also die younger. This means carbon dioxide positively impacts growth, but negatively impacts the lifespan of our evergreens. Given that trees release carbon dioxide when they die, some analysts worry about a potential reversal of the sinking effect of forests.
4. Greening deserts
Meanwhile, ‘carbon dioxide fertilisation’ is making deserts increasingly green, having a greening effect on the most arid places on our planet. From 1982-2010 there has been an 11% increase in foliage cover of arid areas in Australia, North America, the Middle East and Africa. This greening process induced by carbon dioxide has led some to pursue ideas of foresting deserts.
In summary of all these complex issues and interactions, we can conclude that trees absolutely do absorb carbon dioxide from the atmosphere and hold on to more of it than they release at any point in their lifespan including death and decay. Faster growth and shorter lifespans do not demonstrate a proven reversal of the sinking effect. In fact, carbon dioxide may lead to potentially faster growing tree planting zones including in arid areas such as deserts.
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