Tuesday, 9 April 2013

Biodiversity protects plants

If there's one thing that Mother Nature hates more than an empty space, it's a monoculture ;and according to recent research, one of the reasons for this self-defence.

Consider the great British lawn, the vegetable plot or the farmer's field, or indeed, anywhere where humans try to grow just one type of plant; Mother Nature will always do her utmost to introduce some other species. We call them weeds and fight like billio to get rid of them screaming "they're competing for water and nutrients, they must die!"

A wildflower meadow with many plant species all mixed in together
Now think about a more biodiverse space, perhaps a border in a cottage garden or maybe a wildflower meadow. There may be an occasional rogue plant but so long as the overall plant population is fairly dense and the nutrient levels in the soil are well balanced and sensible, it's unusual for weeds to be problematic.

a critter that might become a pest elsewhere is not a major
problem in a biodiverse meadow
Likewise, pests and diseases don't seem to get out of hand. It's almost as though some of the plants just don't get noticed by predators and pathogens. Whilst slugs, snails, aphids and pigeons decimate my vegetable patch, they all visit my mini -meadow and some seem to dwell there, yet the sward stays thick, robust and healthy.

On a green roof, where poor  planning and lack of maintenance results in a monoculture, it would only take one season of really bad weather or an attack by pests that thrive on the single remaining species to kill off all of the vegetative layer.

A study by biologists at the University of Guelph finds that greater species diversity in an area helps ecosystems avoid irreversible collapse after human disturbances. The team compared areas of mostly grasses with areas of mixed grasses and native plants. In a ten-year study plots were selectively burnt. The scientists found that seemingly stable single species grassland plots burned most intensely, collapsed after one growing season and were subsequently overrun by tree species.

The mixed grass and native species plots were less likely to burn intensely and resisted the tree invasion.

So have farmers and gardeners been getting it all wrong by cultivating single species plots to improve yields? Hard to say really.  It all depends who you're talking to. In the vegetable garden (and in the flower garden) I'd say yes.....it is possible to grow marigolds alongside carrots to avoid carrot-fly or nasturtiums with beans to distract aphids.  But, having been married to a farmer for a very long time, I'm pretty sure that companion planting wouldn't be practical on a field scale.

Scientists may tell us that a few extra species in a field of peas or wheat will prove advantageous in the long run but they're not the ones driving the harvesters or trying to store the crop.....modern technology has helped keep food prices down but it only works well where the crop is a monoculture and that means using selective  herbicides and pesticides. It would be wonderful if we could feed the world by foraging, hunting and simple farming and gardening - but we won't achieve the volumes and prices would be humungous.

large fields and huge machines lead to economies
of scale and allow for cheaper food production
May we should shrink the machines, divide up the prairie sized fields and return to medieval strip farming....ie a strip of wheat will be bordered by peas on one side, beet on the other side. We'd see a radical change in our countryside and food production would become very, very expensive. 

It seems as though the preservation of our biodiversity can only be tackled practically and effectively by gardeners, local authorities, highways departments, railway companies, buildings managers and developers. Let the farmers grow food but continue to encourage them to allow woodland, hedgerow, roadside and meadow plants to thrive.  In the meantime, we'll do as much as we can to reinstate green spaces and flower beds, to create green roofs and plant as many different plants species as we can in every bare space.  The bees will certainly thank us. And as a result, the plants will protect our food supply, our wildlife and.......the other plants.
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