Ecosystems at Risk: Limestone caves
6. The nature and rate of change which affects ecosystem functioning

A characteristic of dark cave ecosystems is the lack of change, they are very stable environments. As a consequence of their long evolutionary history, cave animals have reduced their capacity to withstand environmental changes, they have lost resistance to survive an environment which changes. There are no daily or seasonal climatic variations and it is permanently dark. Many animals cannot withstand temperature or humidity fluctuations. A study of adult cave beetles and cave cricket eggs found that as cave soil dried from 100% relative humidity to 99%, the mortality increased from near zero to almost 100%. (R. Buecher, Monitoring the Cave Environment, 1995)

When compared with the size of other ecosystems, cave ecosystems are very small. Many cave animals are known from one site only (endemic). Caves are sometimes considered "island" communities with few if any links to other caves so if organisms become extinct in one cave system, they cannot be recolonised from other caves.

Caves themselves form very slowly and are in a delicate balance with both the outside and inside environment. Slight variations in the movement of water, the concentration of carbon dioxide in the catchment soils or in the cave air, determine whether a cave keeps enlarging by the dissolution of limestone or whether the reverse occurs with the growth of speleothems.

Caves interact with the groundwater so are part of the water cycle. Anything that changes the water cycle in the surface catchment of caves will impact on the caves. Changes to catchment hydrology by the clearing of land, diversion of water, soil erosion and water pollution are major threats to caves.