Do gardeners have an over-fertile imagination?
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With news of the sinking of the chemical tanker Ece off Guernsey, carrying 10,000 tonnes of phosphoric acid, one wonders what effect such a cargo might have on the marine environment. It seems that we need not be too worried – even Greenpeace have said “with a slow dilution, the phosphoric acid should not pose a long-term problem”, although they rightly draw attention to the more serious matter of the fuel oil on board. But as the story broke, the BBC had a quote from a Guernsey man which caught the Ranger’s eye.
Guernsey oyster farmer and marine biologist Mark Dravers said the phosphoric acid could actually benefit the marine environment. He said: “It is one of the fertilisers we use in the medium for growing algae. The effect could be to fertilise the English Channel and benefit all our scallops. There could be some acidity around the ship, but generally I don’t think there’s anything to worry about from an environmental point of view.”
The Ranger is no fisherman but something seems odd about this. It’s not impossible to imagine that in the vastness of the ocean 10,000 tonnes of such a relatively benign chemical as phosphoric acid does little harm. But it is quite another to suggest that it might actually benefit the natural marine ecosystem. To be fair, the BBC uncharacteristically put the words ‘benefit the marine environment’ into Mr Dravers’ mouth, but overall the message seems to be a rather misleading one. Is it a good idea to fertilize natural systems? The Ranger would say decidedly not – and perhaps it’s time this persistent myth was settled.
What do you learn when you’re doing a bit of gardening? How to grow plants. It’s not hard; you just need a nice, soft, fertile soil, a hole, some water and a plant or two. If you want super plants, why, you need to fertilize the soil. A bit of manure dug in, or some of that Tomorite fluid in the watering can and the little plants will be even greener and lovelier. It’s also a good idea to pull up any pesky weeds that pop up around the plants. The urge to cultivate plants is a strong one, culturally deeply rooted in us. But there’s a problem. Putting down fertilizer and cultivating the environment just doesn’t work with natural ecosystems – in fact, it can do a lot of harm. The understandable urge to ‘garden’ natural systems often leads to trouble, and in this case the trouble can be serious. The idea of eutrophication can seem counterintuitive to some – but it’s very important. If you fertilize a natural ecosystem, you do not normally improve it. More fertile soil or water usually results in a decrease in biodiversity, a loss of less common species, and can even change a fresh-water environment into a poisonous one which can even affect humans. When the Ranger plants a tree in his garden, there’s usually a bit of fertilizer put in the bottom of the pit. But he knows he’s going to be around to look after this tree and cut down the weeds around it. So the fertilizer will benefit the tree but anything else that gets benefited too will be removed by hand. However, when he plants out many thousands of trees on say, a reclaimed landfill site, he looks for the poorer and more impoverished soil because this is the best for establishing new trees – although the trees don’t grow as fast the other grasses and herbs around don’t either, and eventually you get better trees. Weed control is very important in establishing new trees, so when you plant some, don’t forget to come back and weed them for at least three years.
The same problem can occur in a natural system if fertilizer is introduced. Weak organisms are smothered by more vigorous ones, when might then use up all the fertilizer and die – leaving neither weak nor strong organisms. You end up with fewer species and less diversity. Certainly the natural order of things is upset. This is true for any natural system. Some of the rarest habitats and most unusual and interesting species are found in places where nutrients are very scarce – sand dunes, chalk downland and heathland in this country for a start. Carnivorous plants, too, those fascinating things, evolved their extraordinary lifestyle to cope with low nutrient environments. If fertilized, such species and habitats are destroyed or die. So, to get back to the Ece tanker and the effect of its cargo on the seabed, one can only assume that the same applies to the habitats and organisms which live on the seabed near Guernsey. The Ranger suggests that although 10,000 tonnes of phosphoric acid in the sea may not be harmful, it is probably misleading for the BBC to suggest that it could ever be ‘beneficial’. Low-nutrient environments need to be conserved, be they on land or in the sea. Save the fertilizer for the garden.