Researchers Explore Climate Change Effects on Species Associations

Climate changes are beginning to reorder species from Argentina's grasslands to the ice-free regions of Greenland.

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A team of researchers from the University of Wisconsin–Madison and Aarhus University in Denmark have published a paper detailing their new research, in the September 19 issue of Nature Climate. The study highlights where and how new combinations of species will probably emerge as a result of changes in precipitation and temperature. In addition, the study consists of global maps of novelty that offer testable predictions. They also carry significant implications for land management planning and conservation.

For example, the results of the study suggest that the new species are likely to gorm in boreal Asia, Amazon, Africa, South American grasslands, and North American Great Plains and temperate forests as a result of changing climate, and will probably increase with increase in climate novelty.

The scientists believe that there will be a widespread reshuffling of species into new environments as species distribution and abundances change. Their prediction is based on the expected increase of global temperatures from 2.5°- 8°F by the end of this century, compared to the 1.5 degrees of global warming experienced in the last century.

We’re identifying three distinct ways that climate change can lead to community reshuffling.

John “Jack” Williams, a UW–Madison professor of geography and director of the Nelson Institute Center for Climatic Research.

Climate novelty is one mechanism where new climates that do not have any historical equivalents emerge. While certain species have already adjusted to these new climates, others have not.

The speed of climate change is another mechanism, this may cause reshuffling amoung species that differ in their capacity to handle the pace of change.

The final mechanism is climate divergence. The differences in the climate variables in the spatial direction of change can affect the species by pulling them in various directions.

For example the upper-treeline species of the Rocky Mountains are affected by variables such as winter severity, growing length of seasons that are based on temperature. The lower treeline species, however, are affected by moisture availability. When the temperature increases the upper treeline species may migrate upslope to cooler regions, and the lower treeline species may move in the opposite direction based on whether the area becomes drier or wetter.

The scientists mapped the three mechanisms individually and collectively with climate data spanning from 1901 to 2013, showing that each mechanism has a diverse spatial pattern.

This clarifies the regions where novel species are likely to emerge as a result of climate change, providing a comprehensive picture of how precipitation and temperature can direct species in separate directions. It can also assist researchers in determining the places where a mismatch between slow species response and rapid climate change can lead to reduction or even extinction of species.

The holistic perspective of the study can inform the decisions made in boardrooms and conservation groups worldwide on how the wilderness can be managed in an era of changing climates.

We know from the past that species are going to move in response to climate change, we know that species are going to probably move in different directions, but the challenge is we don’t know which species can do well in novel climate spaces and which ones can’t. And probably some will do better than others.

John “Jack” Williams

For instance, a lot of mammals and birds may be capable of migrating immediately when faced with rapid climate change, and stay in climates favorable to them. But trees which are limited by their long generation times and seed dispersal distance, and amphibians that have specific microhabitats cannot move during rapid climate changes and may struggle.

Alejandro Ordonez, currently with Aarhus University began this research when he was a Climate, People and the Environment Program (CPEP) postdoctoral fellow at UW–Madison from 2010-13. He is now the head of the team of researchers.

Ordonez developed new techniques for determining rates of climate change, climate novelty and the interplay between these aspects, when he was at UW. Ordonez and Williams published a research applying these techniques in Wisconsin and on a global scale. They evaluated the combined speed of land-use change and climate in the U.S with UW-Madison professor of forest and wildlife ecology, Volker Radeloff in 2014.

This latest research was initiated to find answers that were left unanswered in the previous endeavors.

“So far, my work with Jack and others at UW focused on the ‘how much’ question, but I had no clear idea of the ‘where to’ aspect of these changes,” Ordonez explains. He realized the need for an integrated assessment framework, and incorporated his own and other researchers’ concepts and the recent developments in the field, enabling the evaluation of where and how novelty can emerge.

“Such an assessment allows us to develop hypotheses regarding what will be the principal mechanism that could push a region, a protected area, or a particular community to a novel environmental playing field,” Ordonez says.

Williams states that as the study employed historic climate change data. The predictions made can be tested by researchers. “In principle, these are places where we can go out now and look for novel communities emerging in response to climate changes of the 20th and early 21st century.”

In the Upper Midwest and Wisconsin, regional climate gradients consist of a moisture gradient from west to east and a strong north-south temperature gradient, as the west is generally drier. Therefore, with increase in temperature species are expected to migrate north while other species may move west or east as a result of precipitation changes.

For instance, in another study conducted by UW–Madison doctoral candidate Jeremy Ash, professors Tom Givnish and Don Waller from the botany department, the plant species were found to be moving northwest in Wisconsin. The researchers resurveyed hundreds of places throughout the state, which were initially sampled by UW’s John Curtis in the 1940s and 50s.

This recent research adds to an increasing research body called the climate metrics, which summarizes the ecological risks of climate change, and would be of use to land managers and conservationists. The results contain on-the-ground applications for management decisions. The authors’ note of the study emphasizes the need for adaptation planning and localized management.

For example, if high rates of climate changes are predicted for a particular site, then conservation biologist may need to undertake species dispersal or consider helping in the relocation of vulnerable or slow-dispersing species. Symptoms of climate novelty may need a different management response that can handle ecological surprises.

“That may be more of a monitor-and-watch kind of situation in the sense of it’s a bit hard to know what will happen, so you really want to see what’s happening on the ground,” Williams says.