Mission 2007 - Hydrocarbon Potential Evaluation Team

Maintenance of permafrost - in relation to oil exploration

A layer of moss or lichen acts as an effective mulch, retaining moisture in the upper layers of the soil. Mosses and their undercomposed remains are particularly efficient in thermal insulation when dry, thus restricting heat penetration into arctic soils in summer. When wet and frozen in winter, their effect in reducing heat flux away from the soil is reduced. The net effect of mosses in decreasing soil temperatures in summer is generally greater than the converse effect in winter, and over much of the Arctic the distribution of permafrost is positively correlated with that of mire vegetation underlain by mosses. Thermocarst resulting from destruction of the vegetation by the summer use of tracked vehicles during early stages of arctic oil exploration demonstrated the importance of the moss layer in maintaining permafrost, which is an important habitat for many other species naturally occuring in Alaska as well as ANWR. Destruction of such vegetation can lead to extensive melting of permafrost, both directly and by accelerating the decomposition of organic matter.

Apart from maintaining the natural permafrost habitat, mosses, and also lichens, provide microenvironments of vital importance for invertebrates, and in some communities for the establishment of vascular plants although the relationships may be complex. Lichens release compounds capable of supressing the growth of associated vascular plants and bryophytes. Sphagnum spp. control the environment of mires by lowering pH, by releasing H+ ions in exchange for other cations, and creating waterlogged, anaerobic conditions to which only a characteristic range of other organisms is adapted.