Fresh water is a resource that may also grow scarce

The Times - Ecologists warn the planet is running short of water

Humans currently use about half the renewable and accessible fresh water. While most of it is returned to the ecosystem, the water used in industry and agriculture can be significantly degraded enough so that it may take a long time to recharge or become usable in a less accessible location. Studies done suggest that water-resource management has played a role in many of the conflicts and wars experienced over the past 500 years. Also of note are some calculations on how many liters of water are used in producing foods and household items, e.g. to produce a typical hamburger requires about 2,400 liters of water.