Within Britain there is a considerable range of geographical diversity in ecosystems, determined largely by major climatic gradients and geographical differences in physiography and geology, which in turn shape the pattern of variation in soil development, human activity and land use.

From south to north there is an overall latitudinal decrease in mean temperatures, and from east to west a general increase in oceanicity, i.e. decrease in temperature range, radiation and insolation, increase in precipitation, atmospheric humidity and wind speeds. These main gradients are complicated by the distribution of high land, which is concentrated in the north and west of Britain. High ground causes an increase in precipitation, atmospheric humidity, cloud cover and windiness, and decrease in mean temperature, giving local gradients which reinforce the major gradient of increasing oceanicity. The mountainous districts of western Britain, especially in Snowdonia, Lakeland, Galloway and the western Highlands and islands are thus extremely oceanic in terms of wetness, cloudiness and windiness. However, the latitudinal lapse in temperature results in a south to north gradient, from the warm oceanic climate of south-west England to the cool oceanic conditions of the north- west Highlands, Orkney and Shetland.

The warm and sunny south coast areas of England, especially in Dorset, Devon and Cornwall, give the nearest approach to a Mediterranean climate in Britain, whereas the most continental conditions are found in eastern districts which lie well away from the sea, from East Anglia to the north-east Highlands. While there is a general decrease in mean temperature with distance northwards, the coldest part of Britain in winter is not in the extreme north of Scotland, but in the central and eastern Highlands, which contain the largest mass of high mountain land. Duration of snow cover is a factor of increasing importance with increasing latitude and altitude on our mountains, and also attains its greatest influence in the central and eastern Highlands.

The major climatic gradients combine to give a general increase in severity of conditions for plant growth in a northwesterly direction. This tendency is reflected in the downward shift of the altitudinal zones of vegetation in upland country (forest and scrub, dwarf-shrub heath, montane grasslands and moss-lichen heaths) in the same direction. Over Britain as a whole, there is also a parallel between regional differences in climate and composition of the flora and fauna. One way of describing this is in terms of representation of the biogeographical groupings of species associated with different climatic regimes on a continental scale; another is according to changes in floristic composition of vegetation types, and their associated animal communities. Regional gradients in climate within Britain are reflected in the distribution of plant and animal species, both in presence/absence terms, and in abundance and performance. In general, there is a decrease in the number of species of flowering plants and animals with increasing distance northwards and, to a lesser degree, westwards. Some groups of invertebrates, notably those associated with sunny climates (e.g. butterflies, dragonflies) are especially poorly represented in the north of Britain. On the other hand, the cryptogamic flora of ferns, bryophytes and lichens is much richer in northern and western areas than in the south and east, for these plants are adapted to cool and humid conditions.

Geological accidents have given a prevalence of younger, softer rocks and low-lying terrain in the south and east contrasting with older, harder rocks and mountainous country in the north and west. Calcareous rocks are likewise erratically distributed, consisting mainly of belts of Chalk and Jurassic limestone in the south and east, and tracts of Carboniferous and other limestone in the north and west. Non- calcareous rocks cover a much larger area of Britain. This is an important pedogenic factor since most naturally occurring British soils are characterised by having calcium (Ca2+) as the predominant exchangeable cation (base), and therefore the main determinant of soil pH, but the nutrient quality of derived soils depends almost as much on topography and climate as on the original composition of the parent material. Except on local areas of acidic and porous sands and gravels, which often have deep podsols, the soils of the lowlands are mostly base- saturated and therefore usually fertile brown earth types with mull humus, even though free lime may not be present. Free lime is characteristic of soils formed from chalk and limestone but true rendzinas are very local in Britain. Whilst base-saturation and pH usually give a measure of overall soil fertility, and affect such processes as litter-decomposition and nitrification, some highly calcareous soils are relatively infertile through deficiency of available nutrients such as nitrogen and phosphorus. Raw soils with low nutrient exchange capacity occur on a variety of rocks and deposits, and in many different situations. Peats in the lowlands are mostly of a fen type, formed under the influence of base-rich ground water and a eutrophic vegetation. Only very locally are there lowland raised mires and valley mires with a base-poor peat developed under an acidophilous vegetation.

The lowlands also have a variety of alluvial soils which are usually base-rich. Coastal lands have moderately to strongly saline soils in a variety of situations, including not only stabilised marine sediment but also ground above high water swept by salt spray and solid particles. Spray and sand deposition can cause other mineral enrichment, and many coastal dune systems have highly calcareous deposits where there are numerous shell fragments in the sand.

Soils in northern and western Britain, especially the uplands, show a more marked bias towards podsolic types with mor humus, which on permanently waterlogged ground has characteristically developed into a thick layer of acidic blanket peat. Base-rich soils are often confined to flushed situations where there is a local downwash and deposition of particles and nutrients from above, and the heavy rainfall results in extensive occurrence of gley soils where lateral drainage waterlogs the surface layers especially of glacial drift covering the lower slopes and valleys. On the higher mountains there is a prevalence of skeletal and immature soils which reflect both climatic severity and gravitational instability, and the effects of solifluction are often pronounced.

In Britain, the flora of base-rich and especially calcareous substrata is almost invariably much richer in number of species than that of base-poor types; as the former are so much more local, and often subjected to selectively heavy exploitation, their conservation value is particularly high. Human influence has often been particularly marked on and through the soil. Deforestation, draining, ploughing, burning, grazing, peat-cutting and the addition of both natural and artificial fertilisers have all had a profound effect, in nearly all parts of the country. Their influence includes both reduction and enhancement of soil fertility.