You have likely heard about the general trends that scientists are sure will occur as a result of climate change: plants and animals will be driven out of their native habitats. The ice sheets will melt and the sea level will rise. Extreme weather events, such as droughts and storms, will become more common and more severe.
But go further and ask about the effects of those changes in the environment (in plants, animals and ecosystems in general) and the certainty fades. "There has been an investigation into weather extremes for several years, but it is the investigation of the impacts on the environment that is now catching up with that," said Stephen Thackery.
Thackery is a lake ecologist at the UK Center for Ecology and Hydrology, and is part of a team that published a new study in the journal Global Change Biology on the effects of extreme weather on freshwater ecosystems. * He and his colleagues discussed how storms can alter communities of phytoplankton, or algae, in lakes.
Humans depend on freshwater ecosystems in myriad ways: drinking water, fishing, recreation. Entire regional economies depend on lakes that draw tourists to their shores. A cloudy lake, or one outgrown by the dangerous cyanobacteria of blue-green algae, threatens safety and livelihoods. If we can better predict how extreme weather will interact with lakes, local leaders can use that information to inform adaptation measures and potentially prevent ecological and economic disasters.
Unfortunately, the scientists' search yielded little data that could answer that question in the first place. And the reports they found varied too much from one to another to draw firm conclusions.
One problem: When scientists have looked at the effects of storms on lakes, they haven't been looking at the whole picture. Some storms bring strong winds, some bring heavy rains, others bring both. These events have direct impacts on lakes, such as agitating the water and altering the water temperature. But storms also have indirect effects on the lake's ecosystem by flushing sediment, fertilizer, and other pollutants from the entire basin. "The lakes are like bowls that trap everything that happens within the watershed," said Jason Stockwell, an aquatic ecologist at the University of Vermont who led the project.
In the study, Stockwell and his colleagues propose a framework that takes into account both direct and indirect effects. They hope that future researchers will take that approach rather than isolate and study an interaction, such as the way the wind on the lake's surface disrupts phytoplankton communities.
One of the reasons this type of multivariate approach has been slow to develop is that the technology for measuring all potential effects of storms, physical, biological, and chemical, is still relatively new. Long-term lake monitoring projects tended to collect data on different aspects of the ecosystem on a weekly or monthly basis, not often enough to capture what happens in the water during and immediately after a storm. Without that resolution in the data, it is difficult to separate whether an observation can be attributed to a storm or whether it is due to some other factor, such as a seasonal change.
There is evidence that researchers are already changing their methodologies to address this gap. Stockwell's colleagues at the University of Vermont are participating in a long-term research project called Basin Resilience to Extreme Events, or BREE. They are taking that holistic basin-scale approach to studying the relationship between extreme weather, including storms, heat waves, cold waves and droughts, and harmful algal blooms in the Champlain lake, which spans the entire length of the Champlain Lake. Vermont's western border with New York.
BREE really takes the framework presented by Stockwell and his team one step further, integrating policy and governance into their assessment model. "I can imagine a future state where we can send a broadcast advising farmers not to spread fertilizer or manure over the next week because we expect heavy rainfall," said Chris Koliba, professor of community development and applied economics at the university affiliated with BREE. "That's what this kind of work is beginning to reveal."
Stockwell said that over the past decade or so storm research has already accelerated in other fields, such as land ecology, and that aquatic cologists are starting to catch up. Now that he has seen what little has been established, Stockwell's next project is working to try to determine what the “normal” seasonal trajectory is for phytoplankton communities so that when a storm passes, he and other researchers have a better understanding of whether the changes in communities are due to the storm or are part of a natural progression.
"In freshwater systems, I think it's really starting to take off now," Stockwell said. "This document is synthesizing and integrating a large amount of information that I believe will be a resource."