What are the problems created by a country having a large population growth rate?

The example I will use is the UK. One strategy the government has used is to increase the retirement age so people are working longer.  Males and females now have an equal retirement age of 65 and it will be increased to 67. This helps them to cope with an ageing population as it means that more tax is being paid so the government have more available money and it also reduces the need for as many pensions as people are working longer.  Another way is by increasing the length of maternity and paternity leave. This will encourage people to have children so that there are future workers to balance out the ageing population. The future dependency ratio will decrease and more economically active people will contribute to the economy. In the UK, women can have up to 52 weeks statutory maternity pay which may encourage people to have more children as they have a long length of time with their baby before they have to return to work. A new law where men can have up to 26 weeks paternity pay has also been introduced so that men can also have the responsibility if the woman wishes to return to work.