Earth 2100: prepare for a very different planet

Higher than ever and further rising. That’s what greenhouse gas emissions are, which may lead to a global average temperature rise of 4°C to 7°C within the next 100 to 150 years, scientists have warned. The last time we saw such a dramatic shift was during the previous Ice Age. And if this worst-case-scenario trajectory remains on course, we will have totally different vegetation on Earth, researchers explain in a new paper published in the journal Science.

Based on a comparison of changes that took place between 21,000 and 14,000 years ago, a team of researchers studied fossils records from 594 places around the globe to explore vegetation changes that took place during the last Ice Age. These findings allowed them to predict potential future changes under different degrees of warming in different places around the globe.

The study is one of a kind. While previous research relied mostly on modeling, it has been the first one to look for answers in the deep past, using paleoecological data as a reference point. Connor Nolan, a lead author of the study from the University of Arizona, explains this in plain language: “We used the results from the past to look at the risk of future ecosystem change” and “[a]s temperatures rise, there are bigger and bigger risks for more ecosystem change.”

And we should expect not only new species’ composition but also a total reconfiguration of ecosystems. Forests would become grasslands, grasslands would turn into deserts, rich biodiversity sites would lose most surviving species. The study also predicts that these adverse changes would be far more severe than previous studies have suggested.

The extreme nature of transformations will be due to the rate of temperature rises, which will be truly unprecedented. According to another author, Stephen T. Jackson, “We’re talking about the same amount of change in 10-to-20 thousand years that’s going to be crammed into a century or two.”

The outcomes may prove even more drastic, as warming ecosystems, invasive species and habitat fragmentation may create reinforcing feedback loops, speeding up the process and leading to more frequent extreme events. Jonathan Overpeck, from the School for Environment and Sustainability at the University of Michigan, warns that such changes would also put pressure on many ecosystem services, including water and food provision, recreation and carbon storage.

The probability of drastic changes in vegetation cover is 60% for most parts of the globe. Achieving the Paris targets might lower the probabilities to around 45% for species composition and 30% for structural changes; however, many species would still struggle to survive and many would go extinct. Thus, the stakes are higher than ever as our own survival depends on the very composition of ecosystems we inhabit. Now, it is up to us to speed up sustainability transition we so desperately need.