a) 7 billion
b) Farming reduces the amount of land available for other animals and plants.
i) Waste can pollute water from sewages, by fertilisers from farms and toxic chemicals from industry.
ii) Air we breathe may be polluted with smoke and poisonous gases eg sulphur dioxide due to waste
iii) Herbicides and pesticides on farms are toxic chemicals and affect land. Also it can be affected with industrial waste such as heavy metals. These chemicals can be washed from land and into the rivers.
2. If the population ever grew too big nature would have put things in balance. Lack of food, diseases, build-up of waste products and predators would have reduced the population.Now we are able to grow more food.Treat and cure diseases.We also have no natural predators.
b)We are also using land for building houses,Industrial sites,roads and shops.We are also using acres of land for farming.In quarrying we dig up acres of land for the resources such as metal ores and rocks.
The human population drains up resources of the earth. Raw materials are being used up such as non-renewable materials like oil and natural gas.
Also once metal ores are dug up they cannot be replaced.
3.The ever increasing human population causes numerous problems when it comes to pollution.Once example is herbicides and pesticides during farming,they affect our water supplies because they enter the sewage.Herbicides and pesticides are only needed because our growing need for farming to increase food supplies.Another example is our need for fossil fuels.We are using a lot of raw materials for electricity and fuels in our home.