260
THE ESSEX NATURALIST
You will be getting the impression that I am against reserves,
but let us look at the other aspect I mentioned earlier. Reserves
can and are being created to preserve a particular type of
habitat. Such reserves automatically perform several functions
at one go, not the least being that they preserve the wild life that
is typical of the habitat. Rarities there may be, but this is inci-
dental, and if they like the habitat, the mere preservation of that
habitat will ensure their continued existence.
The important thing, therefore, is the preservation of an
ecosystem. Strictly speaking this implies the maintenance of a
climax condition, e.g., woodland or heath, and these are relatively
easy to achieve. After all, if climax has been reached, the
system is stable by its own efforts, and any intervention by man
will produce something other than climax. For instance, we
had a piece of woodland that had been left to itself for many
years, and could be considered stable. In an endeavour to
increase the number of species in the ground flora, an area of
the wood was opened up. And sure enough the ground flora
increased for a year or two, and then the wood began to take
over again, and the succession moved once more towards climax
woodland. To maintain the flora associated with the opened-up
conditions, it would be necessary to devote time and labour to
re-clearing at two or three yearly intervals. And the irony of it
all is that the species that had come up so obligingly in the
cleared area, were present abundantly at the edges of the wood
where the trees naturally thin out!
Now, woodland and heath are climatic ecosystems that are
self-sustaining. Rut there are others that, in this country at any
rate are not. These may be generally grouped as aquatic and
marsh. Before man interfered, much of lowland England was
marsh and meres with rivers sluggishly meandering through
them. The usual ecological principle operates here, the present
plants making the habitat more suitable for the next stage in the
development towards climax. Thus the open water becomes
silted up and gives way to marsh, and this is gradually built up
above the water table, and so passes to dry land, and this then
follows whatever route leads to climax for that area. Rut in
the days that we are speaking of, if meres silted up, the river
would tend to overflow somewhere else and so the meres would
shift to the newly flooded areas. This is no longer so. With
draining and confining rivers by banks and control by sluices,
the marshes and meres have all but disappeared and life in
lowland Britain has become not only possible but even profitable.
There have been attempts to make nature reserves of the
few remaining marshy areas. Wicken Fen in Cambridgeshire is
one such. Rut is it possible? The answer at Wicken seems to be
no. The draining of the surrounding fens has left Wicken as a
raised island above the shrunken plain, and in spite of all efforts,
the water table at the reserve has fallen irreversibly. Much of