Climate change is really complicated. From the Yale School for the Environment, here's an article on how rising carbon dioxide concentrations are so good for plants that some deserts are greening even without increased rainfall:
Southeast Australia has been getting hotter and drier. Droughts have lengthened, and temperatures regularly soar above 95 degrees F (35 degrees C). Bush fires abound. But somehow, its woodlands keep growing. One of the more extreme and volatile ecosystems on the planet is defying meteorology and becoming greener.
And Australia is far from alone. From Africa’s Sahel to arid western India, and the deserts of northern China to southern Africa, the story is the same. “Greening is happening in most of the drylands globally, despite increasing aridity,” says Jason Evans, a water-cycle researcher at the Climate Change Research Centre of the University of New South Wales in Sydney, Australia.
What is going on? The primary reason, most recent studies conclude, is the 50-percent rise in carbon dioxide concentrations in the atmosphere since preindustrial times. This increased C02 is not just driving climate change, but also fast-tracking photosynthesis in plants. By allowing them to use scarce water more efficiently, the CO2-rich air fertilizes vegetation growth in even some of the driest places.
A phenomenon with limits, it is important to remember.
ReplyDeleteAs temperatures and aridity continue to rise, there will come a point where CO2 concentrations become irrelevant, because there's simply not enough water to support life, even with theoretically ideal concentrations.
Perhaps for a few decades, drylands will slowly green. But then they will get too hot, and have too little water, and all that growth will die off extremely quickly. And then the drylands will expand back to their former extents, and after that the green areas will shrink below what they were before, and it will be a vicious form of rebound.
Global drylands are going to increase by the end of the century. Deserts will grow. And arable land will shrink - perhaps offset, to some extent, by the thawing arctic, but that will come with its own dire consequences.