Managing the Environment

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Managing the Environment

Farming and the environment often seem to clash. But it is possible to produce our food without destroying the Earth.

We have to realise that "traditional farming" techniques will work but will give us poorer yields. Food will therefore be more expensive.

But it will mean that we can treat animals better and recreate a "balanced ecosystem", which will continue to produce our food year after year - that is be sustainable.

Surely it must be worth spending that bit more money?

Organic farming is a phrase often used to describe traditional farming practices.

It is becoming increasingly used and with scientific knowledge it is more efficient that it used to be but without being intensive.

There are three main areas included in organic techniques:

1. Using organic fertilisers The faeces of farm animals such as cows contain lots of useful nitrates. Spreading this useful 'muck' back onto fields saves using chemical fertilisers.
2. "set-aside" By replanting trees (reforestation) and allowing the ground to lie uncultivated, erosion of the soil is prevented and the amount of mineral ions in it can recover after each crop.
3. Using biological pest control Using natural predators to kill pest animals. You can even buy or rent hedgehogs to use now!

Now decide which of the three areas above fit each of the following statements. Type in numbers 1, 2 or 3 and mark your answers.

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Many fish farms have been set up in Scotland and Norway as an attempt to stop relying on North Sea oil too heavily.

Their basic design is the same. A large cage or net is floated in a sea-loch or fjord, that is a narrow sea-inlet.

Fish farm

Salmon are grown from artificially fertilised eggs kept in aquarium tanks. When they are large enough they are released into the nets in the sea-loch.

The salmon can swim around inside the cages but cannot escape outside. This together with the large number of fish =restricts their movement. This smaller movement maximises the energy transfer from their food into putting on weight.

The fish are fed a carefully controlled diet of food pellets. If too much is given it falls through the net and is wasted on the floor of the loch. This wasted food and their faeces can pollute the water, so the nets are sometimes moved around within the loch.

In the nets the salmon are protected from their natural predators - seals and seabirds. However, they can suffer from parasites called "fish lice". One way to treat these is to use an insecticide called Dichlorvos. Another, is to put another type of fish called wrasse in with the salmon. The wrasse feed on the salmon's fish lice and keep them clean. This is a good example of biological pest control.

Biological pest control includes any example where an animal is chosen which will eat the pest species.

Advantages over using chemical pesticides:

  1. It can be cheaper.
  2. There are no concerns about using too much and damaging the environment.
  3. You can be specific about which things you kill, rather than just killing every insect including the useful ones.
  4. You can sell edible plants and crops without having to worry about pesticide residues inside them.

The only disadvantage is that you never get rid of all the pests but instead after a couple of years the number of pests will have fallen to an acceptable, lower level.

The following diagram illustrates what happens when a pest is controlled by using a predator against it:

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Notice that in the end, a gentle, undulating pattern develops between the numbers of pests and predators with far fewer pests around.

Greenhouses are great. They let plants grow in nice, warm, sheltered conditions.

As the Sun's rays shine in they warm up because the heat cannot get out as quickly as it comes in. Closing the windows during the day helps to raise the temperature, humidity and carbon dioxide levels. You can change the light at night time too.

All of this helps to speed up photosynthesis and the growth of the plants.

However, there are many pests, which affect greenhouses and just love those nice conditions.

The four main pests are:

  1. Aphids.
  2. Whitefly.
  3. Mealy bugs.
  4. Red spider mites.

What could we do about them?

We could just blast them with chemical pesticides. But that would kill all the useful worms, ladybirds and bees. It would also stay around in the soil and our crop.

A better way is to use specific predators against each one, that is, use biological pest control.

Pest: Biological control: What the predator does:
Aphids Aphidoletes The larvae eat the aphids. Yum!
Mealy bugs Ladybird One type of ladybird attacks and eats them.
Whitefly Encarsia This tiny wasp lays its eggs inside the whitefly so that the larvae can eat their way out. Nice!
Red spider mites Phytoseiulus These tiny red mites attack the red spider mites.
ANIMATION

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