critical ecosystems

The Story of One Cave, and the Bats who Live There

By Vanessa Madden

Myotis sodalis (Indiana Bat)

The year is 1722, French explorer Philipp Renault, guided by Osage Indian legends, emerges from the mist on the Meramec River. Just as the Osage had told him, a large opening could be seen in the bluff above. A cave of gold was waiting to be discovered………. But, as is often the case when French explorers read too much into Osage legends, the promise of gold was never realized. However, the caves along the Meramec River do contain one of nature’s greatest treasures, bats. I doubt the bats made much of an impression on Renault. But at the time, the numerous passageways of this 4.6 mile cavern system undoubtedly provided plentiful wintering and roosting habitat for native bats. Today we know that Missouri caves are home to 14 species of bats (learn about Missouri bats), three of which are federally endangered (Indiana Bat, Gray Bat, and The Ozark Big-Eared). Unfortunately, the cave was not to be left alone. Saltpeter was discovered. Saltpeter was an important resource at the time because it was a key ingredient in gunpowder. What followed was 144 years of mining saltpeter out of the cave, which ended when Confederate troops destroyed a Union gunpowder plant operating inside the cave itself. My guess is that blowing up large amounts of gunpowder was a bit annoying to the bats. Things quieted down a bit after the civil war. The cave was sometimes used by local residents for summer parties and dances. However, people are curious. Word spread of the beautiful features inside the cave. So, in the 1930’s, the cave was opened to the public. Today, tours are conducted year around.

Corynorhinus townsendii ingens (Ozark Big Ear) Wikipedia

Mankind’s use of the cave over the last 300 years has greatly affected the ability of bats to use the cave as habitat. Many of the original entrances and passageways were sealed off, in an attempt to keep trespassers out of the cave. Year around tours have driven the bats into quieter caves nearby. Perhaps the most unexpected threat to the cave ecosystem was the discovery that groundwater contamination at a nearby hazardous waste site was impacting the cave’s air and water quality.

Myotis Auriculus (Gray Bat)

Ironically, all of the historical causes of declining bat populations pale in comparison to the potential affect of a little fungus known as G. destructans or “white-nose syndrome.” Just as its name implies, this fungus has destroyed over 5 million bats in North America, and it is spreading. The human story of this cave is one of adventurers, outlaws, and entrepreneurs. Nature’s story, however, is one of encroachment and loss. Much has been written about the value of bats to mankind. For example, they consume vast quantities of insects (600/hour according to University of Missouri researchers) and pollinate plants. Perhaps more importantly, they have an intrinsic value that we all can recognize. Now, with native bats facing perhaps their greatest challenge yet, we must do all that we can to protect these diminutive creatures. Venessa Madden is a Midwestern girl who grew up playing in creeks and pastures.  Exploring nature motivated her to become an ecologist. She has been with EPA for 14 years, and currently works as an ecological risk assessor.  She is a past winner of EPA’s prestigious James W. Ackerman Award for Ecological Risk Assessment, and conducted a first ever Baseline Ecological Risk Assessment which included evaluating an inhalation pathway for bats.

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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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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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.

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.

Please share this post. However, please don't change the title or the content. If you do make changes, don't attribute the edited title or content to EPA or the author.