Potential Effects of Forestry Operations

The International Union for Conservation of Nature and Natural Resources (IUCN) struck a World Commission on Protected Areas (WCPA) Working Group on Cave and Karst Protection. This Working Group published Guidelines for Cave and Karst Protection in 1997. This document indicates that forestry operations may have an adverse effect on caves.

The dissolution of limestone is moderated mainly by what is happening on the surface and immediately below the surface of a karst area. Clearcutting of forests in a karst area may “radically” change the local hydrology and affect water quality as surface vegetation regulates the flow of water through a karst system. Leaf litter and root systems minimize the amount of water that can infiltrate the soil. Trees can be major regulators of water quantity through their ability to absorb water from the soil and transport it via the xylem. Thus, trees regulate the amount of water available to supply speleothems. Trees are also the major contributors to CO2 levels in the soil as they achieve 20-25% of their

atmospheric gas exchange through root respiration.

The removal of surface vegetation can also impact soil quality and the biological dynamics of the soil (Hamilton-Smith, 2001). This could subsequently alter the water regime within the cave below which, in turn, could impact the microflora resulting in alterations to the entire food chain of cave fauna.

The British Columbia Ministry of Forests (Vancouver Region) undertook research relating to the management of cave and karst resources in forest environments. The report that was issued indicates that impacts to caves and karst from forestry operations depend on the sensitivity of the karst area, the harvesting methods employed, the quantity and quality of forestry roads being built and the associated ecological attributes of the karst area (Blackwell, 1995).

The report indicates that clearcutting, while one the most efficient and cost- effective methods of harvesting, has been associated with the degradation of caves and karst areas in B.C. and around the world. It indicates that the removal of trees is associated with increased surface runoff, sedimentation and woody debris, which can move through the karst system and impact the hydrogeologic, biological and recreational characteristics of the karst area. It reports that clearcutting can alter the aesthetic appeal of a cave site, introduce fuels and pollutants, clear critical habitat at cave entrances, and alter cave temperature, humidity and air flow. However, the report does not cite any literature in which studies were conducted to prove that the microclimate of caves was altered by surface tree removal.

According to this report, other forestry operations that may have potential negative impacts on caves include road development and bulldozing. Road development may fill in cave entrances, causing caves with weak ceilings to collapse, or destroy caves by blasting. The construction and maintenance of logging roads increases public accessibility to the caves, resulting in further adverse impacts on caves and cave fauna.

Bulldozing and clearcutting may have an impact on groundwater and/or surface streams and clearcutting may result in the destruction of habitat that is also used by cave-

dwelling animals (for e.g., bat species that roost in both trees and caves). It may disturb soils, water quality and cause scouring or the siltation of cave passages. This may result in the death of cave-dwelling animals and/or the discoloration of speleothems. Timber cutting, yarding of logs across or dumping of slash in cave openings can plug cave passages. This has the potential to increase the carbon dioxide levels within the caves, which has adverse impacts upon cave-dwelling animals and may slow the growth of cave formations.

Repap Manitoba Inc’s Environmental Impact Statement indicates that access development (road construction and maintenance of primary all-weather roads) and harvesting activities (logging) have “significant/mitigable” impact on bats.

The 1997 Land and Resource Management Plan for the Tongass National Forest (located on the Prince of Wales Island in Alaska) also indicates that forestry operations may have impacts on karst and caves. “On karst landscapes worldwide, timber harvest has led to serious, often long-term declines in soil depth and fertility, in some cases culminating in permanent deforestation”. In karst lands, and as was evident during fieldwork in the Grand Rapids uplands, tree roots extend into cracks of the limestone bedrock. As the roots pump water and nutrients back into the tree canopy, productivity of the site is tied up in this nutrient cycle and in the forest canopy. Once trees are harvested this nutrient cycle is interrupted for a long period of time.

The Tongass National Forest plan also indicates that there is strong evidence that after timber harvesting takes place, there is a large increase in surface runoff. Soils tend to be thin and residual in karst areas, and can become extremely dry once the forest canopy is removed. If harvesting occurs on steep slopes, without proper log suspension,

much of the soil is removed and the slopes may remain as bare rock. If harvesting occurs on flat terrain, as is the case in the Grand Rapids uplands, soil loss can still occur as soils and nutrients move vertically down into the karst system, beyond the rooting depth of vegetation. This is especially true in areas of heavy rainfall and well-developed sub- surface drainage. While the Grand Rapids uplands may not be considered an area of heavy rainfall, it does have a well-developed sub-surface drainage pattern exemplified by the many lakes that drain internally into the “underlying cavernous carbonate formations” rather than through a surface drainage pattern. Cavities in the limestone bedrock that have been found as deep as 80-100 m (McRitchie and Monson, 2000) are also a testament to its well-developed sub-surface drainage. To mitigate these effects, the plan indicates that leaving slash (splinters, chips, uprooted stumps, etc) in the harvested area would help protect the shallow and fragile soils from erosion and drying.