[MCN] Real Estate: "Exceptionally low levels" of subdivision affect life in streams

[Lance Olsen]

Ryan S. King, Matthew E. Baker, Paul F. Kazyak, and Donald E. Weller 
2011. How novel is too novel? Stream community thresholds at 
exceptionally low levels of catchment urbanization. Ecological 
Applications 21:1659-1678. http://dx.doi.org/10.1890/10-1357.1

How novel is too novel? Stream community thresholds at exceptionally 
low levels of catchment urbanization
Ryan S. King,1,5 Matthew E. Baker,2 Paul F. Kazyak,3 and Donald E. Weller4

1-Center for Reservoir and Aquatic Systems Research, Department of 
Biology, Baylor University, One Bear Place #97388, Waco, Texas 76798 
USA
2-Department of Geography and Environmental Systems, University of 
Maryland-Baltimore County, Baltimore, Maryland 21250 USA
3-Maryland Department of Natural Resources, Annapolis, Maryland 21401 USA
4-Smithsonian Environmental Research Center, Box 28, Edgewater, 
Maryland 21037 USA

Key words: aquatic biodiversity conservation, bioassessment, 
ecological thresholds, indicator species, no-analog ecosystems, novel 
environmental gradients, species sensitivity distribution, watershed 
classification

Abstract
http://www.esajournals.org/doi/abs/10.1890/10-1357.1
Novel physical and chemical conditions of many modern ecosystems 
increasingly diverge from the environments known to have existed at 
any time in the history of Earth. The loss of natural land to 
urbanization is one of the most prevalent drivers of novel 
environments in freshwaters. However, current understanding of 
aquatic community response to urbanization is based heavily upon 
aggregate indicators of community structure and linear or 
wedge-shaped community response models that challenge ecological 
community theory. We applied a new analytical method, threshold 
indicator taxa analysis (TITAN), to a stream biomonitoring data set 
from Maryland to explicitly evaluate linear community response models 
to urbanization that implicitly assume individual taxa decline or 
increase at incrementally different levels of urbanization. We used 
TITAN (1) to identify the location and magnitude of greatest change 
in the frequency and abundance of individual taxa and (2) to assess 
synchrony in the location of change points as evidence for stream 
community thresholds in response to percent impervious cover in 
catchments. We documented clear and synchronous threshold declines of 
110 of 238 macroinvertebrate taxa in response to low levels of 
impervious cover. Approximately 80% of the declining taxa did so 
between 0.5% and 2% impervious cover, whereas the last 20% declined 
sporadically from 2% to 25% impervious cover. Synchrony of individual 
responses resulted in distinct community-level thresholds ranging 
from ?0.68% (mountains), 1.28% (piedmont), and 0.96% (coastal plain) 
impervious cover. Upper limits (95% confidence intervals) of 
community thresholds were <2% cover in all regions. Within distinct 
physiographic classes, higher-gradient, smaller catchments required 
less impervious cover than lower gradient, larger catchments to 
elicit community thresholds. Relatively few taxa showed positive 
responses to increasing impervious cover, and those that did 
gradually increased in frequency and abundance, approximating a 
linear cumulative distribution. The sharp, synchronous declines of 
numerous taxa established a consistent threshold response at 
exceptionally low levels of catchment urbanization, and uncertainty 
regarding the estimation of impervious cover from satellite data was 
mitigated by several corroborating lines of evidence. We suggest that 
threshold responses of communities to urban and other novel 
environmental gradients may be more prevalent than currently 
recognized.

-- 
********************************************************************************************
"The death knell for the grizzly in the Southwest was tolled not by a 
church bell but by a train whistle."

"Changing economic conditions, new homesteading laws, and cheap rail 
travel resulted in an ever-increasing influx of settlers, who 
eventually penetrated to the remotest corners of the region."

David E. Brown.  The grizzly in the southwest. University of Oklahoma 
Press. 1985. p. 97


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://bigskynet.org/pipermail/missoula-community-news_bigskynet.org/attachments/20150706/da5e62c1/attachment-0002.html>