#154 Conservation of species, recycling sewage and paper

Koala is an endangered animal.

Conservation is the process of looking after the natural environment. Conservation attempts to maintain or increase the range of different species living in an area, known as biodiversity.

#153 Pesticides, herbicides, nuclear fallout and non-biodegradable plastics

DDT spraying. 

Some pesticides are non-biodegradable and stay in the environment for a long time. For example, DDT has been a very effective insecticide, used to kill mosquitoes to reduce the spread of malaria. However, because it does not break down, it enters water systems such as lakes, where it is absorbed into plankton. 

#152 Greenhouse gases and global warming

Some gases in the Earth’s atmosphere stop heat radiating into space from the Earth. This is called the greenhouse effect and the gases involved are called greenhouse gases. They include:methane, CO₂ and water vapour. An increased greenhouse effect can lead to global warming and climate change.

#150 Overuse of fertilisers, water pollution by sewage

It is very tempting for farmers to increase the amount of fertilisers applied to crops to try and increase crop yields. However, this can lead to the eutrophication of rivers and lakes and the sequence occurs.