Nav: Home

Envisioning a future where all the trees in Europe disappear

June 21, 2018

Vegetation plays an important role in shaping local climate: just think of the cool shade provided by a forest or the grinding heat of the open desert.

But what happens when widespread changes, caused by or in response to global warming, take place across larger areas? Global climate models allow researchers to play out these kinds of thought experiments. The answers that result can serve as a warning or a guide to help policymakers make future land use decisions.

With this as a backdrop, a team of researchers from the Norwegian University of Science and Technology and Justus-Liebig University Giessen in Germany decided to use a regional climate model to see what would happen if land use in Europe changed radically. They looked what would happen with air temperature, precipitation, and temperature extremes if Europe were completely deforested to either bare land or just ground vegetation. They also considered what might happen if Europe's cropland were converted to either evergreen or deciduous forests.

The researchers knew that climate change impacts tend to be underestimated at a regional level, "because the projected global mean temperature changes are dampened by averaging over the oceans, and are much smaller than the expected regional effects over most land areas," the team wrote in their paper, recently published in Environmental Research Letters. "This applies to both mean and extreme effects, as changes in regional extremes can be greater than those in global mean temperature up to a factor of three."

"We wanted to perform a quantitative analysis of how much land cover changes can affect local climate. Important transitions in the land use management sector are envisioned in near future, and we felt important to benchmark the temperature response to extreme land cover changes"said Francesco Cherubini, a professor in NTNU's Industrial Ecology Programme, and first author of the study. "Decisions regarding land uses are frequently taken at a subnational level by regional authorities, and regional projections of temperature and precipitation effects of land cover changes can help to maximize possible synergies of climate mitigation and adaptation policies, from the local to the global scale."

Future extreme land use changes are not as improbable as you might think. As the global population continues to grow, more land will come under pressure to produce food.

Alternatively, demand for crops for biofuels could also drive what kind of vegetation is cultivated and where.

One future vision of what the world might look like, called Shared Socio-economic Pathways, estimates that global forest areas could change from about - 500 million hectares up to + 1000 million hectares in 2100, with between 200 and 1500 million hectares of land needed to grow bioenergy crops. In fact, the higher end of this range could be realized under the most ambitious climate change mitigation targets.

Changes in land use can have a complicated effect on local and regional temperatures.

When the ground cover is altered, it changes how much water is retained by the soil or lost to evaporation. It can also affect how much sunlight the ground reflects, which scientists call albedo.

The researchers knew that other studies had shown contradictory effects, particularly from deforestation. Some showed that deforestation reduced air temperatures near the ground surface, and increased daily temperature extremes and number of hot days in the summer. Other studies found increases in the occurrence of hot dry summers.

But when the researchers ran their model to see what would happen if land was deforested, they found a slight annual cooling over the region overall, but big differences locally.

Their model showed that when forests were replaced by bare land, the temperatures cooled by just -0.06 ? regionally. The cooling was slightly greater (-0.13? regionally) if the researchers assumed that forests were replaced by herbaceous vegetation. In some locations, cooling can exceed average values of -1 C.

On their own, these regional changes may not seem like much. But when the researchers looked more closely at how these changes were distributed across the region, they found that there was a cooling in the northern and eastern part of the region, and a warming effect in western and central Europe. They also found that deforestation led to increased summer temperature extremes.

"Regional cooling from deforestation might look counter-intuitive, but it is the outcome of the interplay among many different physical processes. For example, trees tend to mask land surface and increase the amount of solar energy that is not reflected back to the space but it is kept in the biosphere to warm the climate," said Bo Huang, a postdoc in the Industrial Ecology Programme who was one of the paper's co-authors. "This particularly applies to areas affected by seasonal snow cover, because open land areas covered by snow are much more reflective than snow-covered forested land."

The researchers found an annual average cooling across the whole of Europe, but with a clear latitudinal trend and seasonal variability. Despite the average cooling effects, they found that deforestation tends to increase local temperatures in summer, and increase the frequency of extreme hot events.

When the researchers ran their model to see what would happen if cropland was replaced by either evergreen or deciduous forests, they found a general warming in large areas of Europe, with a mean regional warming of 0.15 ? when the transition was to evergreen forests and 0.13 ? if the transition was to deciduous forests.

Much as in the deforestation thought experiment, the researchers found that the changes were stronger at a local scale, as much as 0.9 °C in some places. And the magnitude and significance of the warming gradually increased at high latitudes and in the eastern part of the region. Areas in western Europe actually showed a slight cooling.

Cherubini says that understanding how regional vegetation changes play out at more local levels is important as decision makers consider land management policies to mitigate or adapt to climate change.

"It is important to increase our knowledge of land-climate interactions, because many of our chances to achieve low-temperature stabilization targets are heavily dependent on how we manage our land resources," Cherubini said. "We need more research to further validate and improve the resolution of regional climate change projections, since they are instrumental to the design and implement the best land management strategies in light of climate change mitigation or adaptation."

Norwegian University of Science and Technology

Related Climate Change Articles:

Mapping the path of climate change
Predicting a major transition, such as climate change, is extremely difficult, but the probabilistic framework developed by the authors is the first step in identifying the path between a shift in two environmental states.
Small change for climate change: Time to increase research funding to save the world
A new study shows that there is a huge disproportion in the level of funding for social science research into the greatest challenge in combating global warming -- how to get individuals and societies to overcome ingrained human habits to make the changes necessary to mitigate climate change.
Sub-national 'climate clubs' could offer key to combating climate change
'Climate clubs' offering membership for sub-national states, in addition to just countries, could speed up progress towards a globally harmonized climate change policy, which in turn offers a way to achieve stronger climate policies in all countries.
Review of Chinese atmospheric science research over the past 70 years: Climate and climate change
Over the past 70 years since the foundation of the People's Republic of China, Chinese scientists have made great contributions to various fields in the research of atmospheric sciences, which attracted worldwide attention.
A CERN for climate change
In a Perspective article appearing in this week's Proceedings of the National Academy of Sciences, Tim Palmer (Oxford University), and Bjorn Stevens (Max Planck Society), critically reflect on the present state of Earth system modelling.
Fairy-wrens change breeding habits to cope with climate change
Warmer temperatures linked to climate change are having a big impact on the breeding habits of one of Australia's most recognisable bird species, according to researchers at The Australian National University (ANU).
Believing in climate change doesn't mean you are preparing for climate change, study finds
Notre Dame researchers found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage.
Older forests resist change -- climate change, that is
Older forests in eastern North America are less vulnerable to climate change than younger forests, particularly for carbon storage, timber production, and biodiversity, new research finds.
Could climate change cause infertility?
A number of plant and animal species could find it increasingly difficult to reproduce if climate change worsens and global temperatures become more extreme -- a stark warning highlighted by new scientific research.
Predicting climate change
Thomas Crowther, ETH Zurich identifies long-disappeared forests available for restoration across the world.
More Climate Change News and Climate Change Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at