The birds and the trees: Scientists use remote sensing data to help explain patterns of life
Like watching a familiar play, but this time from the balcony and with a new set of binoculars, satellite remote sensing technology is giving Michigan State University researchers a powerful lens to view landscapes that set the stage for earth’s biodiversity.
“Geodiversity, or the variations in abiotic processes and features of the landscape such as landmarks, topography and unique soil types, have yet to be quantified at different scales in the United States,” said Phoebe Zarnetske, assistant professor in the Department of Integrative Biology in the MSU College of Natural Science and principal investigator of the project. “We wanted to know if, thanks to advances in satellite remote sensing, we could measure geodiversity in a new way and align it with already established patterns of biodiversity."
“We are especially interested in the scales at which geodiversity and biodiversity relate most closely,” Zarnetske continued. “Is geodiversity more closely related with biodiversity at fine resolutions, at a plot scale for example, or does it correlate better if we zoom out to a larger area?”
As lead investigator of MSU’s Spatial and Community Ecology Lab, or SpaCE Lab, Zarnetske and her team used open source data from NASA satellites to conduct the innovative research recently highlighted in the paper, “Beyond counts and averages: Relating geodiversity to dimensions of biodiversity” and introduced last year in an earlier paper, “Towards connecting biodiversity and geodiversity across scales with satellite remote sensing,” both published in the journal Global Ecology and Biogeography.
“We would expect that places with more habitat variability provide more unique opportunities for more species, and thus foster higher levels of biodiversity,” Zarnetske said. “But this relationship is likely to depend on the type of geodiversity, the type of organism, how we measure biodiversity and the scale of the analysis.”
Zarnetske, along with former MSU postdoctoral researcher Quentin Read and a team of scientists involved in the NASA-funded working group, tackled the monumental task of quantifying geodiversity variables at different scales, from plot size up to 100 km across, by applying a “ruggedness” index in novel ways.
“We applied ruggedness not only to elevation, but also to many other environmental variables, including temperature, precipitation and plant productivity,” said Read, now a postdoctoral fellow and data scientist at the National Socio-Environmental Synthesis Center in Maryland. “We also applied a diversity index to geological age and soil type categories to complete the picture of geodiversity.”
Next, the scientists tapped into two biodiversity surveys, providing them with tens of thousands of long-term records: the North American Breeding Bird Survey, an annual United States Geological Survey program that began in the 1960s, and data from the U.S. Forest Service’s Forest Inventory and Analysis records.
“We discovered there is not a linear relationship between geodiversity and biodiversity — it really depends on the scale,” Zarnetske said. “For example, topographic diversity was more closely related to tree diversity as you increase to intermediate scales, around 50 kilometers. Understanding scale-dependence is essential for predicting patterns of biodiversity across space.”
“Climate is generally thought to be the most important driver of biodiversity, but we found that geodiversity variables predict biodiversity more consistently,” Read added.
The researchers also found that patterns of biodiversity play out differently depending on where you look and how closely. The United States is made up of several ecoregions —areas dominated by a single, well-defined ecosystem type with its own natural history —and relationships between geodiversity and biodiversity vary across those regions.
“We think the lack of consistency across ecoregions really highlights the importance of both regional context and scale in how the nonliving environment shapes the diversity of organisms on the landscape,” Read said.
Zarnetske and her team have provided scientists with tools sensitive to how variation in region, elevation and topography interact with the organism of focus — tools that have important implications for conservation programs operating under climate change.
“The issue with climate change is that the protected areas we have set aside to conserve biodiversity are going to experience such different climate conditions that, after a while, they won't necessarily match up with the habitat of the species they are intended to protect,” Read explained. “Our research can help point to regions with high geological and topographical diversity, which is associated with a high diversity of microclimates, to maximize the chance that some suitable habitat will be preserved.”
Other scientists involved in the project include: former postdoctoral associate Annie Smith, who helped develop the R package “geodiv” for the project; Kyla Dahlin, assistant professor in the Department of Geography, Environment and Spatial Sciences; Andrew Finley, professor in the Department of Forestry; and former postdoctoral associate John Grady.
The work was funded primarily by NASA and conducted in collaboration with an international team of scientists as part of the NASA working group, bioXgeo. Additional funding was provided by the National Science Foundation and the USDA’s National Institute of Food and Agriculture.