Page 38 - ALG Issue 2 2023

biodiversity
Increasing
Biodiversity
on the
Allotment
There are three aspects to biodiversity; a well-tended allotment can improve and conserve all three without compromising on crop yields or quality.
The first factor that contributes to biodiversity is genetic diversity – the variation in the gene pool. We can increase and maintain genetic diversity by growing a wide range of varieties rather than sticking to just one. This is particularly important for those plants that reproduce asexually (cloning),
for example potatoes and garlic. The vulnerability of relying on one cultivar (monoculture) was clear in the awful famine in the 1840s when potato
blight struck Ireland. One third of the population starved, and another third emigrated. Fortunately for us, seed catalogues list many varieties of plants, so keeping a high genetic diversity on our plots is very straightforward.
The next factor is species diversity. Again, this comes naturally to allotments as we grow a wide range
of species of plants on our plots. Most pests and diseases attack a single species or a few closely related ones (the exceptions are pigeons and slugs, generalists that can eat a wide range of species). By growing a wide range of different species, we limit pest damage and ensure that even if one crop fails, others will still produce. Traditional crop rotations help to reduce pests and diseases, especially in soil. Pathogens
can build up in soil if the same species is grown there year after year; so again, more diversity gives more health and resilience. Wildlife will also benefit from a wide range of species. Having
a bed of flowers, especially those that attract bees and other pollinators, such as borage, will enhance your plot. Soft fruit also attracts pollinating insects and inevitably some gets ‘shared’ with songbirds.
Thirdly, habitat diversity is a major contributor to biodiversity. Increasing the range of habitats on our sites may need coordination with your society or council. Creating a pond, for example, might need permission and risk assessments, and maintaining a diverse boundary hedge is not something an individual plotholder can often take responsibility for.
Well-managed boundary hedges are great for biodiversity. They may also improve site security. A diverse
Increasing the range of habitats on our sites may need coordination with your society or council
hedge will contain many species of trees, shrubs, and wildflowers, so that different types of birds and insects
can find food, shelter, and nest sites. Blossom in the spring, camouflage from predators, berries in the autumn and shelter from winter weather are
all usefully provided by a hedge. Hedge maintenance will improve diversity; hedge-laying looks very destructive but studies have shown an increase in bird populations two years after the most drastic treatment as the hedge thickens out.
Things we can all do include having a compost heap, a small pile of rotting logs and nest boxes for birds, allowing a patch of longer grass to grow (as in the no-mow May campaign).
Biodiversity isn’t a bed of roses! Sometimes the wildlife can frustrate our efforts. One example on my own plot are the moles who excavate in inconvenient places. I take this as a sign of good
soil health; the moles are after the worms which are very plentiful on my plot because I add mulch and practise no-dig. Predators are a good indicator species that there is a diverse and healthy food web to sustain them.
Soil is a huge part of biodiversity. Healthy soil is teaming with life. Worms are the obvious example, and it has been estimated that there is more worm protein under a pasture than livestock above it. There are many different worm species, but worms are just one of the more visible creatures under our feet. It
38 Allotment and Leisure Gardener