Term name Description
Ice AgeA period of time between 2.4 million and about 13 000 years ago when the climate in the British Isles became very cold, several times, with intervals (interglacials) when temperatures were as warm as at present
IgneousCrystalline rock formed from cooling of molten magma: plutonic, if solidifies below the surface; volcanic if solidifies above the surface
Integrated land use managementA means of managing land uses together in a way that maximises their potential, while at the same time causing minimum damage to the environment and, where possible, enhancing it
Improved grasslandGrassland to which manure or fertilisers have been added, or which has been ploughed and/or reseeded to improve the quality of the grass for stock
Informal recreationRecreational activities that are not organised in any way, carried out by individuals, friends or families
InfrastructureThe built structures supporting a development or industry – buildings, transport, drainage, etc
InterglacialThe period between two ice ages/glacial periods
InversionThe process by which, although temperature generally falls as altitude increases, cold air becomes trapped. Particularly common in valley bottoms, forming thick mist/fog, with warm air above – thermal uplift is prevented
InvertebratesThese are species without a spinal column ie worms, jellyfish, insects.
Institute for Terrestrial Ecology (ITE)a UK government–funded research agency with its Scottish base at Banchory, Aberdeenshire. Carries out research into anything related to terrestrial ecology. Now called the Centre for Ecology and Hydrology (CEH) since merging with the Institute for Hydrology
Isostatic uplift

This is the rise in the level of the land relative to the sea caused by the relaxation of Ice Age conditions. It occurs when the weight of ice is removed as temperatures rise, and the landscape is raised to form raised beaches.