The geology tells us this was part of the route of the Thames which was formerly a reasonably
fast-flowing river, so its bed was sands and gravels. The Thames now runs further south,
and is a bit slower. The younger terraces of sands and gravels are now about 5 to 3 0 metres
above sea level, with a southerly aspect. Many areas have been worked by mining companies
to provide materials for the building trade. Conservationists used to throw up hands in
horror at major disturbances of this sort, but it is now widely recognised that the diggers
and bulldozers are not all bad, and that the mineral extraction sites can actually make a
useful contribution to biodiversity by increasing the variety of habitats.
So these areas have nutrient-poor sandy soils, which dry out in the warm summer sunshine,
and are easily disturbed by feet of people and rabbits (not to mention the bulldozers!).
This means that most of the plants are drought-stressed and nutrient-stressed, so they
are often small in size and include more than usual annuals, with drought-resistant
perennials, grasses and many members of the Pea family. The Pea family (clovers,
medicks, vetches etc) get nitrogen compounds through the bacteria that fix atmospheric
nitrogen in their root nodules, so they tolerate low soil nitrate levels better than most
other plants. Some lower plants, such as mosses, liverworts and lichens, also flourish
here, including a few uncommon species. Where lakes are part of the landscape, these
also are low in nutrients allowing simple plants like Stoneworts to flourish, at least until
nutrient enrichment happens, as it inevitably does eventually.
Our very own Peter Harvey recently published a report of a survey he had undertaken
looking at the invertebrates in five areas in the London Borough of Havering, in this
Thames Terrace area. Peter found that many of the insects and spiders are uncommon
and include a large number of Red Data Book species and Nationally Scarce species. I
have found that some of the many plants found in these areas are uncommon too. The
animals flourish in the dry conditions, with plenty of bare sandy places for burrows or
nesting sites and the diverse plants provide forage foods. It is clear that these habitats,
although ephemeral in the sense that they do not stay this way forever, need only simple
conservation measures to ensure some continued soil disturbance for the special flora and
fauna to survive. These sandy areas are slow to scrub over, or develop trees, apart from a few
Silver Birch, so they can last quite well with not too much expensive maintenance. Occasional
rotovating or scarifying of the ground is needed in different areas to maintain some open
ground. The disturbance factor also applies to many other important wildlife habitats in this
country. However, planting grasslands and then mowing to make lawns is very damaging,
and tree planting is nearly as bad. The close sward and the increasing shade give no open
sunny bare places that the plants and invertebrates need to survive. Sadly, although much of
this landscape is now set aside for public access, it has been managed and landscaped for
lawns and trees, and the value to the scarce wildlife has dropped steeply as a result. Of
course, the land set aside for leisure does not necessarily have wildlife conservation as a
primary aim, but when some of the sites are as precious as this it is worth trying to combine
the two aspects.
Essex Field Club Newsletter No. 42, September 2003
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