Longer droughts, harder rains, shorter winters, shallower snowpack: This is a list of life in the West these days, as farmers and city folks alike deal with increasing weather extremes. And what do those weather extremes mean for both marine and terrestrial ecosystems? It turns out they could mean plenty.

New research funded by the National Science Foundation shows that climate is increasingly controlling synchronous ecosystem behavior, in which species rise and fall together. The study was recently published in the journal Global Change Biology.

Ivan Arismendi, an aquatic ecologist and assistant professor at Oregon State University, is a study co-author who says rising climate variability is a concern given that extreme weather events, including prolonged droughts or heat waves, can disproportionately impact biology, reduce resilience and leave a lasting impact. Arismendi explains that an increase in the synchrony of the climate could expose marine and land organisms to higher risks of extinction.

He notes that there has been a lot of research on climate change, but most of that work has been focused on trends in average conditions, such as rising temperatures. “However, climate is also predicted to become more variable, and very little research has addressed this issue. Our study found that extreme variability is synchronizing processes within and among ecosystems at a level not seen in the last 250 years,” he says.

An interdisciplinary research team, led by the University of Texas Marine Science Institute, documented that wintertime atmospheric conditions along the West Coast, known as the North Pacific High, are important to marine, terrestrial and freshwater ecosystems in California and the Southwestern United States. A strong wintertime North Pacific High is associated with winds favorable to marine productivity, but also blocks the onshore storm track and leads to drought on land.

Rising variability
Researchers documented that the North Pacific High has become more variable over the last century, and that these trends have been imprinted on physical and biological indicators, from the continental slope to the Sierra Nevada and beyond. There are more dramatic and frequent swings in this winter climate pattern. They documented that not only has variability increased, but also synchrony among diverse ecosystems.

Bryan Black, associate professor of marine science at the University of Texas at Austin, is the lead author on the study, and he noted researchers found that land, rivers and oceans are all strongly related to a winter climate pattern off the western coast of North America, and that this pattern has become more variable over the past century. “This extreme variability is increasingly imprinted on these freshwater, terrestrial and marine systems, and this has caused them to become more synchronous with one another, with a number of implications for fisheries, drought, snowpack and tree growth.”

It turns out that tree ring chronologies offer much longer histories than the observational records available, and corroborate that variability and synchrony have risen over the past 100 years — and to levels as high as any observed in the past 300 years.

More frequent and larger changes in the North Pacific High appear to originate from rising variability in the tropics and are linked to the record-breaking El Niño events in 1983, 1998 and 2016, and the 2014-15 North Pacific Ocean heat wave known as “The Blob.”

Arismendi is an assistant professor in the Department of Fisheries and Wildlife in OSU’s College of Agricultural Sciences. Jason Dunham, an aquatic ecologist at the U.S. Geologic Survey Forest and Rangeland Ecosystem Science Center in Corvallis, Ore., is also one of the study’s co-authors.

Understanding what these weather extremes mean to local ecosystems can help farmers, and others, with ways to improve risk management and maintain productivity in the future.

Source: Oregon State University