(^168) an environmenTal hisTory of Wildlife in england
Norwich and Sheffield.^36 The latter, for example, is characterized by colourful
garden escapees, especially feverfew, goats rue and michaelmas daisy, tansy
and golden rod, which in places formed distinctive flowery ‘meadows’. The
river Don flows through the centre of the city, and here – together with
great thickets of Himalayan balsam – Gilbert recorded a number of large
fig trees. These had evidently grown from seeds which had passed into the
river in treated sewage, but what was curious was that they only occurred
in the east of the city – the district associated with heavy industry – and
that none appeared to be less than c.70 years old. Gilbert deduced that the
establishment of the figs:
Coincided with the height of the steel industry. At that time river water
was used for cooling purposes and the Don ran at a constant 20 degrees
centigrade: it was this special microclimate that enabled the trees to
establish in such large numbers. Following the decline of the steel industry,
river temperatures have returned to normal but mature trees are able to
survive.^37
The character of suburbia
These kinds of built-up or derelict landscapes accounted for only a small
part of towns and cities by the 1950s. Much larger areas were occupied
by suburbs, primarily residential in character, in which most houses were
provided with gardens of some kind and within which there was more open
space generally. These districts provided a greater range of habitats for
wildlife: indeed, as Davis showed in 1978, in terms of arthropods the best
predictor of diversity was the proportion of land in an urban area occupied
by gardens and parks.^38 In the period before c.1920 urban and suburban
growth tended to be closely associated with railway lines and stations, and
to a lesser extent with the principal roads, so that built-up areas took the
form of broad ribbons spreading out from major towns, leaving pockets
of open countryside between. Moreover, where land was developed rather
simple grids of roads were laid out and plots usually sold to a multiplicity
of individuals or companies, who often developed them over a period of
years or even decades. In part this was because difficulties in obtaining
mortgages ensured that people at all social levels tended to rent their homes.
Developers thus often leased out the houses they had erected rather than
selling them, ensuring a slow return on their investment and limiting the
amount of money available for further building. Although large-scale and
rapid development sometimes occurred as often as not the transition from
countryside to suburb was thus gradual.
It is important to emphasize that until the middle decades of the twentieth
century, the development of suburbs was not ‘planned’, in the sense that
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