Planes, trains and automobiles
Fragmentation of habitat is an issue which is very much
apparent in this country and the Stour Valley is no exception. In basic
terms fragmentation occurs when a wildlife habitat is divided up and a
change of use or a physical barrier occurs between areas which were once
linked. This severely restricts animal and plant movement and dispersal.
This tends to run hand in hand with habitat loss, where a once large
section of habitat, say chalk downland is carved up with changes in its
use, so eventually only small isolated sections are left.
The barriers can be obvious such as motorways, railways
and urban development or more subtle such as intensive farming or
artificial watercourses. In this country the problem is not a new
phenomenon and has been a direct consequence of agricultural and
industrial development over hundreds of years. The only difference is
these days the obstacles are on a grand scale. Wherever a motorway passes
it always causes irreparable damage to the environment and cuts off vast
areas to wildlife, which has little or no chance of crossing the obstacle.
This partition leads to a loss of species diversity. As
the habitat shrinks so does the viable population, particularly the higher
up the food chain you go as these creatures need a larger range to
survive. In order to keep a healthy population new genes need to be
introduced which is increasingly difficult as the habitat becomes
isolated. Statistics show that in early spring mortalities on roads and
railways of male mammals such as badger, fox and otter increase tenfold as
the males seek out new partners and territories. When a population has
become isolated there is a real danger of extinction as many unforeseen
elements can tip the balance. There is also a tendency for the population
to be more susceptible to booms and crashes, as dispersal is limited.
Otters in the Stour Valley face huge obstacles from the
fragmentation of their river corridor habitat. More importantly the
chances of otters from adjacent rivers diversifying the population are
remote. An otter on the River Medway attempting to cross over to seek new
territory on the River Great Stour has quite some assault course to cross!
This includes two A-roads, M 20, main London railway line and the newly
constructed Channel Tunnel Rail Link (CTRL). With male otters commanding a
territory in excess of 50km it comes as no surprise that transport links
are by far their biggest killer.
Organisations like KSCP are working to reverse this
trend by enhancing and, where possible, linking isolated habitats. Agri-environment
projects such as DEFRA’s Countryside Stewardship Scheme offer money to
landowners and farmers to create wildlife corridors in the form of grass
margins, hedgerows and arable reversion. This can provide vital corridors
between isolated habitats. Developers, due to public pressure, are much
more aware of the needs of wildlife. Badger and amphibian tunnels, fencing
and reflectors are a more common feature in the construction of roads and
railways. A great example is the millions of pounds that CTRL have spent
on the construction of mammal bridges over the new route. Let's hope that
our remaining wildlife habitat is extended and not further fragmented.
Jason Adams, Ashford Countryside Officer
