New research from scientists at the University of Copenhagen's Department of Geosciences and Natural Resources Management has arrived at troubling conclusions based on an analysis of vegetation trends over the past decades. Their findings are reported in the journal Nature Sustainability.
Professor Rasmus Fensholt of the Department of Geosciences and Natural Resource Management explains the consequences of vegetation patterns in different regions of the world. "We observe a clear trend of arid areas developing in a negative direction in the most economically challenged countries. Here, it is apparent that the growth of vegetation has become increasingly decoupled from the water resources available and that there is simply less vegetation in relation to the amount of rainfall. The opposite is the case in the wealthiest countries.”
To arrive at these conclusions, the research team used satellite images of vegetation and rainfall collected over a fifteen-year period from 2000-2015. As lead author, Christin Abel comments, "Here, our results demonstrate that in arid regions, particularly those in Africa and Asia, less vegetation grows for the amount of rainwater that falls, while more vegetation grows in arid areas of South America and Australia." Abel is a postdoc at the Department of Geosciences and Natural Resource Management.
Why do we see this trend? The researchers think that population growth in poorer countries may be the most influential factor, explaining the increasing usage of land for agriculture and the subsequent decline of suitable land in said regions. Meanwhile, the increase of farmlands with access to irrigation and fertilizers in richer countries could account for why vegetation in these regions seem to be more resilient to climate change.
With climate models predicting the expansion of arid ecosystems across the world, this understanding of trends in vegetation resiliency has real-world impacts. "One consequence of declining vegetation in the world's poorer arid regions areas may be an increase in climate refugees from various African countries. According to what we've seen in this study, there is no indication that the problem will diminish in the future," explains Rasmus Fensholt.
Commenting on the overall trend of increasing vegetation that has been documented globally, Rasmus Fensholt says it’s imperative to understand the complexities of the big picture. "We have been pleased to see that, for a number of years, vegetation has been on an upwards trend in arid regions. But if we dig only a tiny bit deeper and look at how successfully precipitation has translated into vegetation, then climate change seems to be hitting unevenly, which is troubling," concludes Rasmus Fensholt.