Lending a Critical Eye to Ecosystems Part 2 – Ecological Significance

By Holly Mehl

Last week I posted my first blog which talked about a project we worked on developing Terrestrial Conservation Focus Areas within Region 7. These areas were developed to provide an additional tool for decision makers to help in prioritizing ecological resources. Today, I want to share a little bit about of the technical side using some maps to demonstrate how we combined each of the different layers to arrive at the Conservation Focus Areas. In an effort to be as simple as possible, I’m going to really just skim over things, but I would encourage you to check out the report for the entire methodology.

Today I will share the first step, the creation of an Ecological Significance layer. To develop this we looked at the percent conversion of ecoregions from historical vegetation (original land cover) by abiotic site type (yes this is a mouthful). The actual methodology is quite complicated but you can think of it as how much natural vegetation is still around. Areas that are currently crop, barren land, urban or water represent areas of significant conversion. For example a reservoir would represent 100% conversion since it used to be a stream valley, while a grassland might exhibit 30% conversion if a third of the area is now covered with trees. You can get an idea of what this looks like by comparing the two figures below (the big gray area in the second Figure is St. Louis, MO).

The layer of percent conversion by abiotic site type (again, for exact details, read the methodology in the report) was combined with the Opportunity Area analysis previously conducted by the Missouri Resource Assessment Partnership (MoRAP). Opportunity Areas are places which are located at least 75 meters into the interior of a patch of natural landcover and which are at least 75 meters away from a road. Think of them as undisturbed areas, with the largest areas receiving a “1” and the smallest areas receiving a “5.” The two layers (percent conversion and ranked opportunity areas) are then combined, as shown below, to produce a measure of Ecological Significance

To me as an ecologist, the Opportunity Areas by themselves have so much value because they point out places on the landscape where development land demand is relative low so the opportunity to pursue conservation management is greater. Because they are defined as natural or semi-natural land cover patches that are away from roads and habitat patch edges, I figured I could look at these polygons in a GIS to see where I might want to purchase land in Missouri. In my mind it would be most attractive to pitch my tent as far away from roads as possible!

In my next post I will discuss how we came up with threats, as well as how we combined Threats and Significance to arrive at Ecological Risk.

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.

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