Exposure Of The Sea-Coast

Except upon lofty hills and mountains no type of vegetation is so much exposed as that of the sea-coast. It is this factor which causes the vegetation to have so distinctive a character, not only as regards height and form, but also in regard to its physiological adaptation to dry conditions. One reason of this exposed character is the relation of the sea to the land. The maritime zones are constantly being exposed to the land and sea breezes, which set up regular air currents periodically. The general absence of trees or of shrubs thus subjects the ground vegetation to the influence of the wind and the other factors.

The winds which blow to the land bring with them salt, which accumulates upon the coastal vegetation, and for this reason the maritime plants are halophytes, or plants adapted to soil in which there is a large proportion of chloride of sodium, as well as some bromides and iodides.

There are also frequent sea-mists, which may be distinguished in this connection from the normal landward breezes, since they do not possess much force, but are characterized by their saturated condition. To these sea-mists may largely be attributed the high percentage of saline matter in the coastal sands, shingles, and salt marshes. Frequently also sand storms are set up which have several different effects, such as the burying of the plants in sand, and the erosion by sand blast of those that are exposed.

The waves also are powerful factors upon the sea-coast, exposing plants to destruction by the erosion of the coast. They also, in the case of land to the leeward of dunes or shingle, have a beneficial effect by making the conditions saline. It is usually when there are gales that such occurrences take place. Thus many factors contribute to the exposure of the sea-coast.

Erosion Of The Coast

One of the most marked features of the present conditions so far as the sea-coast is concerned is the erosion of certain portions of the east and south coasts, and to a far less degree of the west and north coasts.

Whilst there has been accretion or addition to the coast in some areas erosion has been going on from time immemorial. So long ago as the Roman period the Wash area has been protected by banks in order to prevent the farther advance of the sea.

The sea margin is in fact continually changing. Generally speaking, however, a distinct difference exists between the west and north coasts and the south and east coasts. Along the former there has been little destruction, and some addition, whilst on the latter there has been almost generally a depletion of the land, with some exceptions.

This is due to the fact that the older and harder rocks are mainly found on the west and north, whilst the newer and less resistant rocks are found on the east and south. The occurrence of hard rocks, however, such as the chalk, locally, on the east and south coast, as in Yorks, Norfolk, and Sussex, causes the coast to preserve its contour intact, whilst alternating soft bands, often where river estuaries occur, are the areas where the coast has been destroyed. Along the east coast, however, there is a drift of shingle southwards to the Thames, so that some parts are preserved, or there may even be some accretion, as at Blakeney and Lowestoft, and along the Essex coast.