A Risk-and-Impact Matrix for Protecting Rare Cave Animals in a Canal Park's Karst Sites

Chesapeake and Ohio Canal National Historical Park is a thin strip, 184.5 miles long and on average only 290 yards wide. It holds what the authors call the most important tract of land in Maryland for preserving rare, threatened and endangered (RTE) subterranean macroinvertebrates, but apart from rain, the water reaching it depends almost entirely on land use outside the park. A research team asked to help park managers developed a scoring matrix to decide which sites need protection first. This article summarizes their account in Park Science, by Dorothy J. Vesper, David Smaldone and Daniel J. Feller.

Why the park's caves are vulnerable

The park runs along the Potomac River in Maryland and the District of Columbia, and 161 perennial streams and hundreds of intermittent ones cross it. It is home to more than 10 RTE groundwater species, such as cave-dwelling amphipods and isopods. The authors say its narrow shape and the shift of surrounding land from farming to housing make it especially exposed to groundwater pollution that starts outside its boundaries.

Karst landscapes form because their rocks dissolve, which produces caves, springs, seeps and sinking streams. Surface water can reach the groundwater quickly, so pollution can follow. The authors list manure and sewage, leaves dumped into sinkholes, trash and pesticide runoff, septic leaks, extra sediment, paving over recharge areas and groundwater pumping, along with damage from recreational cavers. Because cave and spring habitats are isolated from each other, their animals have evolved into separate communities, and low populations, low reproduction and long lives make them vulnerable. The article adds that cave- and groundwater-adapted animals make up more than half of the imperiled (G1 or G2) species tracked by state natural heritage programs in the United States.

The Federal Cave Resources Protection Act of 1988 requires inventory, documentation and protection of karst resources on federal land, and lets managers withhold cave locations that shelter sensitive species.

The data behind the matrix

• Inventory: 76 karst sites, of which 59 are on park land, including springs, seeps, streams, caves and mines.
• Water chemistry: 45 samples. The major elements were similar across sites and showed no water-quality problems from inorganic substances.
• Species surveys: focused on priority sites, mainly in spring 2012 with more sampling through 2015, in 28 sampling efforts. The team updated records for 11 RTE species and found seven new locality records for cave-dwelling animals, but did not find several of the rarest species previously documented, which may reflect loss of those species or poor conditions on the day.

How the matrix works

The matrix compares two scores for each site and sorts sites into four quadrants: high risk with high impact (the most important to protect), low risk with low impact, and mixed cases that need more evaluation. It is built as a spreadsheet so that it can be edited as priorities change.

Each risk factor was scored from 0 to 10, with the worst case at 10, multiplied by a weighting factor, summed, and divided by the highest site's total so that scores run to 100. Where data were missing, and for the weights, the team relied on professional judgment agreed with park specialists. Impact scores were summed across the species at each site and normalized the same way. Sites with notable cultural, geologic or other biological resources received special marks.

What it found

• Risk scores ran from 100 down to 46, with a mean of 75. Nearly all sites scored above 50% for risk. Chemistry and industrial land use scored zero everywhere. The highest-risk sites combined the presence of water with farmland in the buffer, and in the top-scoring group, visitor access also scored high for the upper half.
• Four of the five highest-ranked species are "Only Known Occurrence" species at the state or global level.
• Some species are still undescribed. One amphipod, Stygobromus n. sp. 14, is likely a global "Only Known Occurrence" found at one site. Records of a subterranean millipede, from one park specimen and two others in Washington County, suggest the area is near the northern limit of cave millipedes in the eastern United States.
• Seven of the 26 locations evaluated fell in the high-risk, high-impact quadrant, and two of those scored above 75 out of 100 on both. The park identified them as management priorities.

Limits

The authors say the model is only as good as its data and that its point values and weights should be treated as preliminary. It can be adjusted when new data arrive, for example if more RTE species become listed. They suggest other parks with karst resources could build similar matrices, and say the spreadsheet is available on request with instructions.

Sources

• Dorothy J. Vesper, David Smaldone and Daniel J. Feller, Park Science article on vulnerability of sensitive karst habitats at Chesapeake and Ohio Canal National Historical Park, National Park Service; rewritten in hubnx's own words. The imported title was cut off, so a new one is used. The article's figures and conflicting site counts are left out.