image: One study of spatial synchrony from the early 2000s examined two populations of musk ox on opposite sides of the Greenland Ice Sheet. Even though they were separated by 1,000 miles of ice, their populations fluctuated in sync — they had good years and bad years at the same time.
Credit: Hannes Grobe/Wikimedia Commons
LAWRENCE — Populations of animals and plants separated by even thousands of miles can rise and fall together driven by ecological factors, a phenomenon scientists call “spatial synchrony.”
A new study from the University of Kansas in Ecology Letters reveals the study of spatial synchrony over a long enough timescale leads to better testing of ideas, improved statistical results and new conceptual realms for understanding ecology, conserving species and farming more profitably.
“There are many examples of this,” said lead author Daniel Reuman, professor of ecology & evolutionary biology at KU and senior scientist with the Kansas Biological Survey & Center for Ecological Research. “One study from the early 2000s examined two populations of musk ox on opposite sides of the Greenland Ice Sheet. Even though they were separated by 1,000 miles of ice, their populations fluctuated in sync — they had good years and bad years at the same time.”
Reuman said his study reviews the most important conceptual developments in spatial synchrony over the past 20 years.
“One of these is timescale structure,” he said. “Populations don’t just fluctuate — they do so on multiple timescales simultaneously. They might change on an annual basis, as expected, but they also fluctuate on decadal scales and beyond. The causes of these fluctuations vary, and synchrony can differ depending on the timescale.”
Along these lines, Reuman and his co-authors found studies focused on longer-term timescales could be considerably more valuable to scientific understanding than those with shorter time considerations.
“If you have a study that lasts 20 years, it’s more than twice as valuable as a 10-year study,” he said. “The value increases exponentially. We wanted to highlight ways that long-term scientific monitoring efforts in our field have led to paradigm shifts in conceptual understanding. We feel really fortunate to study on the backs of some of these long-term monitoring projects, many of which have been ongoing for decades. We wanted to highlight what that does for scientific understanding and the importance of supporting those efforts moving forward.”
According to study co-author Max Castorani from the University of Virginia, the findings add a new element to value of long-term environmental research.
“Studies lasting several decades are rare in science but play an outsized role in generating knowledge,” Castorani said. “Our new synthesis further demonstrates that sustained investment in long-term ecological studies yields breakthroughs in understanding the natural world and its influence on society and industry. This leads to big gains in informing policy and management related to the environment, from climate and weather to forestry and fisheries.”
Lawrence Sheppard, a co-author from the Continuous Plankton Recorder Survey, said, "The advantage of having long-term data on plankton abundance is twofold: With the right techniques, you can get good statistics about repeating seasonal changes in the data and also uncover long-timescale changes in the oceans."
Reuman said figuring out the environmental drivers of synchrony is another important line of inquiry in the new study.
“Years ago, researchers had decent theoretical ideas about what caused synchrony, but those ideas were largely untested in real populations,” he said. “In only a few cases could they definitively pinpoint a cause. Today, thanks to better tools and long-term datasets, scientists can make more accurate inferences about the factors driving synchrony — provided they have sufficient data. Because different causes can influence synchrony at different timescales, researchers must analyze data accordingly to identify the drivers effectively.”
The KU researcher said the drivers and effects of synchrony, along with how synchrony itself operates, can change over time. The theoretical frameworks described in the study have led to a more granular understanding of human-driven global warming as environmental changes are predicted to come faster in coming years.
“The third major trend we look at involves changes in synchrony,” Reuman said. “This ties to long-term monitoring efforts. If you need a certain amount of data to detect synchrony, you need even more to detect changes in it over time. These changes have increasingly been linked to climate oscillations, which in turn are connected to climate change. Scientists have studied the effects of climate change in many ways, but only recently have we recognized that changes in large-scale synchrony patterns can be another consequence of shifting climatic variables.”
Lastly, Reuman and his co-authors examine research trends into the mechanisms of synchrony — factors that influence synchrony in ways that might not be immediately obvious. These mechanisms are varied and require detailed study of long-term data to uncover.
Reuman’s co-authors were Vadim Karatayev and Nat Coombs from KU; Jonathan Walter, Ethan Kadiyala, Amanda Lohmann, Kyle Haynes and Max C.N. Castorani from the University of Virginia (with Walter also affiliated with the University of California-Davis); Lawrence Sheppard from the Marine Biological Association of the United Kingdom; Thomas Anderson from Southern Illinois University Edwardsville; and Lauren Hallett from the University of Oregon. Karatayev is also affiliated with the University of Maryland.
Reuman said the value of understanding spatial synchrony went beyond purely scientific inquiry. Work on synchrony could help farmers predict outbreaks of disease and pests or know when market prices might be apt to rise or fall based on climactic factors unseen without a grasp of synchrony.
“You can imagine this in an agricultural context,” he said. “In a study from 2016, we examined population synchrony in aphids, a major crop pest. When aphid populations synchronize across a region, it means pest outbreaks occur simultaneously in multiple areas, potentially reducing crop yields across the entire region.”
Beyond pests, synchrony can also affect crop yields themselves, Reuman said.
“For example, if all corn farms in Kansas experience a poor harvest in the same year, less corn will be available on the market, impacting prices,” he said. “However, if some farms have a bad year while others do well, they balance each other out. The first scenario represents synchronous fluctuation, while the second is asynchronous fluctuation. The same concept applies to disease outbreaks. Whether populations are synchronous or asynchronous can have significant consequences depending on the context.”
Journal
Ecology Letters