Get access to the common mistakes students make in their A-Level physics exams. Inspired by The Examiner's reports this is an un-missable opportunity to find out where precious marks are dropped.
Farming is often under-rated nowadays. Modern farming practices have radically increased the efficiency of farming, producing more food from the available land.
In a lifetime we have moved from not having enough to eat to having tons of food.
Despite this "intensive farming" providing us with masses of cheap food there are a number of problems.
Strain can be placed upon domestic animals so that they produce the best possible food yield for us. Examples include the confinement of battery hens and veal calves.
Food chains are damaged by the use of pesticides to kill insects and animals that could damage crops. The chemicals used are indiscriminate, they kill any insect. So the links in food chains are wiped out and whole communities of animals can suffer.
Fields that are intensively farmed contain only single crop species, and the crowd of plants, insects, animals and birds that used to exist there are gone. Some face extinction.
Deforestation is the loss of trees due to demand for timber, land and so on.
It doesn't just occur in rainforests, the deforestation happens here too. We have virtually deforested our whole country over centuries, including our hedgerows.
The rainforests are the lungs of the Earth. The rapid rate of deforestation there has critical importance.
What are the effects of deforestation?
There are 4 main effects:
- Decrease in rainfall:less trees means less transpiration and photosynthesis.
- Soil erosion: the exposed soil dries out under the Sun.
- Serious flooding: rainwater runs off the exposed soil rather than soaking in as before.
- More carbon dioxide: the trees that used to remove the gas are gone.
The problem gets worse and worse.
How does what we buy link in to deforestation?
Pesticides are used to kill animal pests, and herbicides are used to kill weeds.
Both can be useful types of chemicals. However, their use has problems.
One problem is "bioaccumulation". These chemicals are poisonous to other animal life. If the animals at the start of a food chain take up small amounts it becomes more and more concentrated higher up until it can kill the animals at the top - including humans.
One example was the use of a pesticide called DDT used in the 1960's. It was used to kill insects (an insecticide) that were damaging crops but it leaked into rivers and contaminated plants. The small animals and fish further up the food chain collected more and more because it wasn't lost (not excreted) from their bodies. Eventually, otters ate the fish and were killed. Otters were virtually made extinct in Southern England.
Eutrophicationis what happens when too much chemical fertiliser is used on crops and it washes into rivers and streams.
The nitrates in the fertilisers are essential to get crops to grow well and increase yields.
However, if too much is used, or it rains soon after it is added to fields, the fertiliser gets washed away. The nitrates then help plants in the rivers and streams to grow very quickly, especially algae.
But after the initial massive growth in algae there isn't enough light and for them all and a lot of the algae die.
All those dead plant start to decay. You are left with a green and slimy mess. This removes oxygen from the water and kills fish and other animals. Then even more algae and animals die.
So farmers have to be very careful using fertilisers so not to wipe out all river life.
The bottom line with all these problems with modern, intensive farming is that to change will be very expensive.
Do we want the environment to be used carefully?
Will we pay more for our food?
Are we prepared to help and do our bit?