Water quality under assault
Urban growth more than just a scapegoat
By Robyn Sanders
Urban development may be having a negative effect on biodiversity in Maryland streams, according to research done by Baylor and the University of Maryland, Baltimore County.
Dr. Ryan King, associate professor of biology at Baylor, and Dr. Matthew Baker, associate professor of geography and environmental systems at the University of Maryland, Baltimore County, worked on the study which was published this year in the online journal Ecological Applications.
Over the course of several years, the researchers analyzed data from streams in Maryland to gauge the impact of urban development in watershed areas on organisms, such as fish, invertebrates and amphibians, that live in streams. A watershed is an area in which all flowing water drains to the same place.
“What we found that was surprising was how sensitive many of these stream-dwelling organisms really were to urban development,” King said. “We were relying heavily on public data sets — that is, landscape data that’s published by federal agencies, and then water chemistry and biological data from the state of Maryland that they generate through their streams.”
The field research was conducted by the Maryland Biological Stream Survey. King said variables such as basic water chemistry, physical habitat and species of organisms were measured in about 2,000 different streams to generate the data he and Baker analyzed.
“The biological aspect of it is the most important because those organisms are interacting with their environment and if there’s certain species that aren’t there that we expect to be there, that tells us that there’s something wrong,” King said. “We were attempting to determine what level of urbanization was leading to the disappearance or decline in these organisms.”
Baker said the unexpected aspect of their findings was the very low levels of urban development at which losses of biodiversity occurred.
“We found that many organisms declined sharply in response to watershed development, even as others responded positively or not at all to the same activities,” Baker said. “However, many groups we expected to be ‘sensitive’ were apparently not so, and others we expected to be ‘tolerant’ were sensitive instead.”
To analyze the data, King and Baker developed a new statistical method called TITAN (Threshold Indicator Tax Analysis).
“[TITAN] actually allowed us to identify a certain level of urbanization in a watershed that resulted in a sharp change in the abundance of different organisms,” King said. “This analysis showed that it was happening at very low levels, and it was happening with many organisms at roughly the same level.”
King said the results of their research could lead to more careful scrutiny and required improvements in urban development.
“There’s actually been considerable interest by the United States Environmental Protection Agency, as well as some nonprofit groups such as the Nature Conservancy, in using this information to help inform decision makers about regional planning, particularly in cases where new developments are being proposed in potentially sensitive watersheds,” King said. “We’re also working with state and federal agencies on how to use the TITAN method to analyze some of their own data to help develop numerical standards for specific chemicals or land use, things of that nature.”
Baker said their analytical method can allow scientists to better understand how different influences affect biological communities and it also may help improve how natural resources and biodiversity are protected.
“Our work implies that widespread land development should proceed with greater awareness of the true consequences for natural ecosystems and the services they provide human society,” Baker said. “Meanwhile, we hope our approach will be used as a model for obtaining more precise information in analysis of biological communities.”
King said their research findings not only apply to organisms in streams, but to human health as well.
“I think beyond just the fact that these are fish and invertebrates that are declining, what they represent is life,” King said, “and when our water is polluted to the extent that things that normally live there cannot, that’s a real warning sign about potential dangers to human health as well.”