Conventional wisdom has held that despite it’s many downsides, a warming planet would be good for plant growth, at least among plants in northern regions. Recent evidence has proven that wrong, quite wrong in fact, as current projections claim that by 2100 we could see as much as an 11% decrease, globally, in the number of days per year that plants can grow.
Northern regions would suffer the least. There would be fewer days with snow or frost, but the extra heat and CO2 wouldn’t actually increase the number of growing days because there wouldn’t be any more sunlight, a factor that previous hypotheses seem to have completely ignored. Sunlight is a strict control on the rate at which plants grow.
The tropics would fare much worse though. As the planets warms up, droughts will become even more common, which could lead to truly disastrous reductions in plant growth days per year. Certainly desert and arid plants would notice little difference, but thirstier plants like trees and pretty much all agricultural production, would suffer.
Some 2.1 billion humans, who rely on agriculture directly for food or for their income, would be affected by such droughts. Reduction in plant growth hurts people directly, since there would be noticeably less food, but also indirectly as numerous ecomonmies are focused on agriculture. The Sahel region of Africa, for example, could see serious famines as plant growth days are reduced by up to 200 days per year, effectively cutting growing seasons in half.
Looking at mitigation factors though, including plans to reduce CO2 emissions and reduce the warming of the planet, things get a little brighter. Researchers discovered that almost any reduction in emissions reduces the impact on plant growth. That’s one more reason for nations and organizations to work hard to reduce emissions, remove carbon from the atmosphere, and switch to greener technology.