Israeli scientists use data from desert to inform on future of areas affected by climate change
The world’s climate is changing, and according to NASA, 19 of the hottest years ever documented have occurred since 2000, with 2016 and 2020 tied for the hottest ever on record.
Double rainbow in the Judean desert. Kfar Adumim Photo by Yaara Gilboa Eyal/TPS
This summer is already making worldwide headlines, with the UK registering 40 degrees Celsius for the first time in its recorded history.
More climate extremes are occurring. Snowmelts affect the high-altitude areas, severe forest fires are increasing, while rain pulses, followed by dry periods, are becoming the norm. If heat waves and severe droughts are trends that will continue to affect the globe, what will the future bring to the forest and cropland regions of the world?
Scientists have been looking at the unique adaptations of desert life, which function by their own set of rules long considered to be unique to dry areas, for years. New research published by an Israeli-led international team of scientists suggests that climate change is causing these “dryland mechanisms” to increasingly affect Earth’s damper areas, such as croplands and forests.
To better predict how the world’s wetter areas will operate in the future, the team recommends that we can begin to apply the lessons learned from how life works in arid regions. The study was led by Prof. José Grünzweig of The Hebrew University of Jerusalem and co-authored by Dr. Omer Tzuk and Prof. Ehud Meron of Ben-Gurion University of the Negev.
The researchers state that their new insights can contribute to advancing methods to withstand climate extremes and lessen their impacts on nature and people.
Spurred by a recent meeting of the European Ecological Federation and an action of the European Cooperation in Science & Technology (COST), the team compiled a list of the unique rules of life driving dryland ecosystems.
Currently, more than a third of the Earth’s land area is drylands. Many of these key processes have been considered relevant only to arid regions, including rapid cycling between wet and dry conditions that influence plant and animal activity, redistribution of water in soils by plant roots, and formation of living crusts on soil surfaces by microscopic organisms.
Overall, the team identified 12 different dryland mechanisms affecting multiple processes, including vegetation distribution, plant growth, water flow, energy budget, carbon and nutrient cycling, and decomposition of dead material. These dryland mechanisms are controlled by environmental factors, such as intense solar radiation, high temperatures, large bare patches between plants, and inconsistent availability of water.
The mechanisms were also categorized as either more likely to be fast-responding – those that we might expect to see occurring from short-term drought, and slow-responding – those that would happen after decades of dry conditions as a result of changes in plant distribution.
The researchers presented these 12 dryland mechanisms that are routine processes in drylands but are not commonly found in wet ecosystems. Then they categorized these mechanisms based on how likely it is that they are going to happen in wetter systems in the future.
What sort of changes would be required to start seeing these mechanisms in wetter systems? What is clear to the researchers is that a new, unprecedented pattern is emerging, one that was considered absent or insignificant in most biomes on Earth. These dryland mechanisms are now, with increasing frequency, occurring in temperate regions. In the future, these will likely increase in frequency and become more relevant due to warmer, drier conditions from climate change.
For example, much of Europe experienced a severe drought and heat wave in summer 2018. As a result, the low plant cover in agricultural fields during this time likely led to desert-like biological processes occurring in these usually wet locations.
A new heat wave is also scorching Europe this summer. Under these conditions, plant growth decreased dramatically in these systems, which lead to more exposure of bare soil on the surface that is not covered by plants.
To better understand potential future ramifications of dryland mechanisms on elements like vegetation distribution and decomposition of dead material, the team took its drylands data and modelled it to show how the forces driving drylands will increasingly apply to temperate regions under future climate conditions.
The results and long-term consequences were “stunning.” For example, their models predict that the total non-dryland area with an average topsoil temperature of above 40C is estimated to increase by about 17 million km2, approximately equal to the total land area of the USA and Brazil, by the end of the century. Furthermore, moisture in the topsoil is expected to decrease in 74% of the global land area currently not classified as drylands.
The researchers note that mathematical models are commonly used to predict how systems will behave under drier or hotter conditions, but it is usually assumed that the operating rules will stay the same even if the climate changes. The researchers then asked: what if the rules by which the system works to change and the established models do not take this into account?
Dry soil conditions will cause the emergence of many dryland mechanisms, such as redistribution of soil water via plant roots. Other mechanisms will respond to changes in vegetation, with more sparsely distributed vegetation increasing the prevalence of organisms forming soil surface crusts, and increasing the role of sunlight in breaking down dead leaves.
Clearly, some of these projected changes will occur in regions with large human populations, and thus, will significantly affect the well-being of society in these regions. The researchers note that they will need continued research on ecosystems under increasing frequency and severity of droughts and heat waves to improve their understanding of the underlying emergent processes.
Ultimately, the researchers hope that a better understanding of these uniquely adapted desert systems will lead society to “set realistic expectations for the future of historically temperate and wetter areas – before it’s too late to heed Mother Nature’s call.”
TPS
