Lending a Critical Eye to Ecosystems – Bringing it all Together
by Holly Mehl
In my last two blogs I talked about our effort to develop Conservation Focus Areas for EPA Region 7, and one of the steps (Ecological Significance) for developing the Ecological Risk portion of our terrestrial assessment. As a reminder the diagram below explains how all of the different pieces of our analysis fit together.
As I mentioned in my previous blog, Ecological Significance is derived from two metrics, percent conversion and opportunity areas. To arrive at Ecological Risk, we need to combine significance with threat. Threats were calculated as the sum of three indices: development land demand; agricultural land demand; and potential toxic release impacts. The first two represent conditions that could lead to conversion of natural land cover to a modified land cover (urban or agriculture), while the third represents known potential sources of anthropogenic (man-made) toxics. The document itself provides a lengthy description regarding the weighting of various parameters and rankings which arrive at the final grid where the lowest threat areas were assigned a “1” and the highest were set at “6.” These threats were then combined with significance to derive an Ecological Risk layer.
Irreplaceability is final metric that is necessary in developing the Conservation Focus Areas. Irreplaceability values for each assessment unit within ecoregions were developed using software called C-Plan (Pressey et al. 1994). Irreplaceability is defined as “the likelihood that a given site will need to be protected to achieve a specified set of targets, or conversely, the extent to which options for achieving these targets are reduced if the site is not protected.” For targets we used Abiotic Site Types (which ensure representation of important habitats), the highest ranked Opportunity Areas, and areas of high vertebrate richness. Again, all of the specific details can be found in the final document.
Terrestrial Conservation Focus Areas were then derived from combining risk and irreplaceability. As shown below, Conservation Focus Areas are those areas (depicted as 30 x 30 meter pixels) which have both high Ecological Risk and high Irreplaceability.
In general, the more natural ecoregions such as the Ozark Highlands, Nebraska Sand Hills, Flint Hills and Cross Timbers and Prairies have more focus areas, whereas areas that are heavily agricultural had fewer. You can access and download a variety of shape files (included both ranked Conservation Opportunity Areas and all Conservation Opportunity Areas) from our analysis here. Simply click on the folder labeled public, then the folder labeled EPA Region 7. Stay tuned in November when I will talk about how we developed Aquatic Focus areas.
About the Author: Holly Mehl is an ecologist for EPA Region 7 who helps with water monitoring in the field and performs mapping for EPA Region 7’s program offices when in the office.
Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.
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