The special ecological
features of Britain are related primarily to geographical and
climatic position in the world. The British Isles as a whole lie in the temperate zone,
but they differ from much of continental Europe in experiencing a strongly oceanic
climate. A climatic regime of this kind is reflected in certain general ecological trends.
The temperature range favours forest, composed largely of broad-leaved, relatively
thermophilous trees, as the climax life-form over much of the country. The moisture
balance, with a general excess of precipitation over evaporation, promotes leaching
of nutrients from the soil, so that podsolisation is a widespread phenomenon, and
there is a prevailing tendency towards development of acidic surface humus
horizons. Where topography also contributes to waterlogging of the soil, peat mire
inhibits tree growth and becomes the climax formation.
The high atmospheric
humidity associated with an oceanic climate satisfies the
needs of many hygrophilous plants; the fern, bryophyte and lichen floras are
especially rich and the British Isles are the European headquarters of many Atlantic
species, including some which have an interesting world disjunction. The equable
temperatures of an oceanic climate also allow the survival locally of southern
thermophilous plants, which reached their maximum extent at the Postglacial
Climatic Optimum, and also of a northern, montane element which cannot tolerate
hot summers, and is a relict flora from the cold Late-glacial Period. Thus, although
the insular position of the British Isles has resulted in a numerically poorer flora than
many European countries, there is a unique blend of different phytogeographical
elements which has given our flora an international distinction. Species of oceanic
distribution which reach their greatest European abundance in Britain include a
number of distinctive community dominants such as ash Fraxinus excelsior, heather
Calluna vulgaris, bluebell Endymion non- scriptus, gorse Ulex europaeus, U. gallii, U.
minor and heath rush Juncus squarrosus. Plant formations of strongly oceanic
character, such as blanket mire and moss heath, are also more extensively
developed in Britain and Ireland than in the rest of Europe, and some plant
communities appear to be unique to this country, albeit usually recognisable as
relatives of various continental types. : :, • . ••.
The Nature Conservancy's
responsibilities did not extend to Ireland, but many of the
important ecological features of Ireland are represented in the west of Britain, which
has a strongly oceanic climate. There is a lesser representation in Britain of southern
Atlantic and Lusitanian species, and no limestone karst country here is quite as fine
and unspoiled as the Burren of County Clare, but on the whole the flora and fauna of
Ireland are less rich than those of Britain.
Faunistically, the
British Isles are internationally important for a number of insular
races and subspecies which have diverged in isolation from the main European
populations ; as the breeding station for large populations of several globally rare and
local birds, especially seabirds; and as the wintering haunts of a significant
proportion of the total world or European population of certain wildfowl (Anatidae) and
waders (shore-birds). The fauna also contains an interesting and diverse
combination of different zoo- geographical elements. The mammal fauna of Britain is
poor in species, partly as a result of extinctions caused by man, and the invertebrate
fauna is much less rich than that of continental Europe.
Although relict elements
of both flora and fauna are well represented, Britain has very
few endemic species of either plant or animal. The British flora and fauna is,
however, interesting for its ecological diversity, as the response to an unusual blend
of climatic conditions within a small area. The particular combination of plant species
in communities is, however, the most distinctive feature of this country, compared
with the rest of Europe.
