When plants are harvested, nutrients are removed from the soil. These can be replaced by natural fertilisers such as manure or by NPK fertilisers containing nitrogen, phosphorous and potassium.
Like all living things, humans exploit their surroundings for resources. Before the beginning of agriculture about 10,000 years ago, small groups of humans wandered across large areas, hunting and gathering just enough food to stay alive. Population numbers were kept low because of the difficulty of finding food.
The development of agriculture led to a population explosion that has accelerated enormously during the past 500 years. Unlike other species, humans can adapt to and survive in almost all terrestrial environments on the planet.
The graph shows that the human population is growing. This is because the birth rate is much greater than the death rate.
In the last fifty years, the population of humans on the planet has increased from 3 billion to 7 billion. This increase is more rapid than at any other point in the history of our species.
The human population is predicted to reach around 10 billion by 2050. As the number of people increases, the yield of food from farming will also need to increase or malnutrition and starvation will occur.
The yield of crop plants per unit area of farmed land can be increased by intensive farming methods, such as the application of chemical fertiliser and the widespread use of pesticides. These methods have the advantage of increasing the quantity of food that can be produced, but can also have an adverse effect on the environment.