A research world under glass: plants, survival, and a changing climate - PART 3 of 3 – Plant responses to a changing climate

When it comes to climate change, there are many unknowns. One thing for sure, however, is that temperatures generally speaking will increase. How plants respond to increasing temperatures will likely vary from species to species and from region to region. Rainforest plants that have large leaves and use the C3 photosynthetic pathway may be at a disadvantage because they simply use too much water and may become subject to excessive photorespiration. To some extent we may see plants change their morphology (e.g. smaller leaves), but very few plants are known to shift from one photosynthetic pathway to another. C4 plants, which are often aggressive colonizers (tumbleweeds, for example), will likely expand in distribution and invade areas currently occupied by C3 plants. CAM plants, on the other hand, will likely remain dominant in hot, arid regions, but because they grow so slowly, their ability to expand will probably be limited.

Research in the Biosphere 2 Tropical Rainforest - where temperature, precipitation, and atmospheric composition can be both tightly controlled and measured - allows us to study a system under glass with more than 100 species of trees and plants living in predicted future-Earth conditions. By altering the drought, temperature, and CO₂ scenarios – and including the soil’s role in ecosystem carbon, energy, and water cycling – we have a better understanding of the physiological responses of rainforest trees and what to expect as our planet continues to warm and weather variation increases. Plant physiology is flexible on much shorter timescales then geographic range shifts or genetically mediated biochemical pathways. However, our Biosphere 2 research findings reveal that physiological flexibility will not be enough to mitigate the rate and scale of human-caused changes to the planet’s carbon cycle. Perhaps not surprising given that our decades-long movement of carbon (fossil fuels) from the earth to the air took hundreds of millions of years to go from the air (CO₂) into ancient vegetation and then into the earth; these rates (10-100 vs 1,000,000 years) are orders of magnitude different and many of today’s plants aren’t, and won’t be, able to keep up.