Forest transition to grasslands just a tipping point away

Accumulating evidence suggests that forests, communities dominated by trees, can quickly become grasslands with only some small changes in the environment particularly temperature (higher) and rainfall (lower), which often vary together. This comes as no surprise because one of the best long-term studies with which the Phactor is familiar, the still ongoing research that has been mentioned in this blog before, the monitoring of tropical forests by David and Deborah Clark, suggests the exact same thing. Tipping points are the big problem that looms by ignoring climate change and pretending that nothing needs to be done. What this means is that nothing much will happen as the trend of temperatures rising and rainfall dropping continues, and then in very short order, a forest becomes a grassland maintained by fire ecology. For a grassland to change back into forest takes falling temperatures and a lot more rain. But for people who live in the area, everything changes, plants, animals, agriculture. And even worse all that carbon locked up in wood gets released in short order, carbon dioxide that will help exacerbate the trend that caused the change. So tipping points will catch humans with their pants down around their ankles even though they are not unexpected. Unfortunately by the time you get to say "I told you so!" to do-nothing politicians it's too late, a cheerful thought.

350? And I thought the answer was 42.

42 was the answer to the ultimate question (What is the meaning of life, the universe, and everything else?). But 350 turns out to be a very important answer (in parts per million) to the question of how much carbon dioxide can be put into the atmosphere before its impact on climate seriously affects human civilization? It doesn't help that human activities have already pushed the CO2 concentration to 385 ppm, so not only must we stop emissions, they must be reduced. And of course human energy demands are not likely to decrease anytime soon.


This article discusses the concept of a tipping point. Many systems will resist change such that factors that influence them seem to only make small incremental changes year by year causing some people to question what all the excitment is about. However, when you reach a certain critical level, the change suddenly accelerates. The melting of Arctic sea ice during the summer has been increasing but by very small amounts as each succeeding year became the warmest year on record. This year the ice melted a lot, and if this is a trend, then watch out baby! That land you own in central Florida may be the next coastal property.



What is even more alarming is when a long-term study of tree mortality suggests a similar tipping point may exist for tropical forests. Trees, those behemoths of biomass, are repositories of CO2. When trees die, their decomposition releases all that CO2. This also happens when humans cut and burn the forest. Tree mortality increases as the average temperature increases probably because while respiration increases as the temperature increases, photosynthesis begins to decline. When respiration exceeds photosynthesis, these woody storehouses of CO2 begin literally respire themselves to death. This is another tipping point system. And if it happens, tropical forests could begin to literally fall apart in a matter of decades releasing all that carbon dioxide which would only accelerate the temperature increase in a positive feedback loop. A grassland would replace the forest, and during occasional or seasonal droughts, grasses are subject to burning. A grassland will have a much smaller biomass than a forest.



If these tipping point scenarios have are true, and the available data certainly suggests they are possible, then the sooner we act the better. Of course those whose depend upon the status quo are actively trying to prevent such actions by arguing the non-existence of tipping points. Explaining the idea of a tipping point to people is critical to motivate people to support and seek changes.

Let's not even consider what will happen to the farm belt in Lincolnland if climate change continues along the predicted trajectory, but suffice it to say, it's ugly.