Since most of the earth’s surface is covered in water it no doubt seems odd to be worried about the availability of water. Of course, this seems less odd when one considers that much of this liquid bounty is too salty for humans to drink or use in most forms of agriculture. When pollution and distribution (people have an irrational propensity to build cities where water is scarce) are taken into account, then the grounds for worry become clear.
While people normally think of water in terms of something we drink, 92% of our water usage as a species is due to agriculture. Plants and animals need water directly, but water is also used for other purposes in the industry. For example, the feed given to animals requires water. In addition to the direct use of water, water is also “consumed” (that is, removed from being useful to humans) by contamination from agriculture. The chemicals and waste of agriculture often ends up in rivers and other bodies of water, rendering it unusable or at least harmful.
Looking just at the direct water costs, the creation of animal “products” imposes the highest water costs per kilo-calorie (kcal). Growing edible roots and cereals requires .5 quarts per kcal, making these foods very water efficient. Fruits are rather more costly, requiring 2.2 quarts per kcal. For meat product, pork is relatively efficient, requiring 2.3 quarts per kcal. Beef is by far the least efficient, using 10.8 quarts per kcal. As might be imagined, the use of water raises both practical and moral concerns.
One obvious practical concern is working out how to efficiently handle water resources as the population increases. Adding to the difficulty of this matter is the fact that economic improvements in developing countries will most likely lead to a significant increase in the desire for meat, especially beef. Given the water cost of meat the agriculture industry will be hard pressed to meet such increased demand especially if the water supply is under even greater strain.
As might be imagined, there are various practical solutions to the technical problems of water. For example, more efficient agriculture would enable more food to be grown using less water. As another example, the development of cheaper means of purifying water of salt or pollutants would help. Obviously enough if the world eschewed meat in favor of plants, then that would have a significant impact on water usage.
The main moral concern is one of distribution. That is, using moral values to determine how the available water will be used and who will benefit from its use. As noted above, the growing of meat and other animal products is water intensive relative to growing plants. While there are practical grounds to moving away from animal agriculture, the decision to do so (or not do so) is a matter of ethics. After all, decisions about who is entitled to the water resources and how these resources should be distributed are moral decisions. If, for example, it is decided that water resources will be allocated to the beef industry, then this means that less water will be available to grow more water efficient foods, thus potentially reducing the food supply while also creating food that is relatively expensive for the consumer.
As the population grows, the moral concerns will become even more serious. After all, it is certainly worth considering that the demand on water resources will eventually be high enough that choosing between growing beef and raising more water efficient crops will be a choice between providing the more affluent few with a luxury food and providing the less affluent many with the food they need to survive.
An obvious counter to this is that we have always managed to find a solution to such problems in the past and hence we will surely find one (or more) in the future. After all, the population doomsdays predicted in the past all turned out to be in error.
While this response has considerable appeal, it is worth noting that there must be a point at which our ability to solve the water problem reaches its limit. After all, the supply of water on the earth is finite and even if we were to use the water with incredible efficiency there would be a point at which the available fresh water could not support a population of a certain size. Naturally, this can be countered by reducing population size—but determining whether we should do this or not and the details of the reduction would involve moral choices.
It is also worth noting that there are many practical (rather than theoretical) problems that could prevent us from adequately solving the water problem. The droughts that affected the United States in 2012 had an impact on food production and if these droughts become more common, then the matter of distributing water resources will become even more pressing. There are also the political considerations, such as political entities controlling the distribution of water to serve their own ends. Even the United States has political conflicts over water distribution and these will probably only worsen as the population increase and water distribution changes as the climate changes.
As a final point, it is worth noting that water is a resource that is almost endlessly reusable. Unlike oil, our use of water generally does not destroy the water. For example, when we drink water we are not digesting it into hydrogen and oxygen to provide energy—rather we use it to hydrate our tissues, remove waste and so on. Roughly put, the water that goes in eventually comes back out. Of course, the water that we use does become contaminated and this contamination can render the water useless to us. For example, while urine is mostly water it is rather unsuitable for drinking. As another example, water that is contaminated with chemicals, feces or radiation is useless for many purposes. Fortunately, we can purify water (although this can be rather costly) and purification also occurs naturally. Unfortunately, we have been rather busy damaging many of the natural purification systems and even more busy contaminating water. Also unfortunate is the fact that being “pro-environment” (favoring the preservation of natural purification systems and being in favor of limiting water pollution) is often cast in a negative light and dismissed by mockery and hyperbole. However, there are very practical economic reasons for preserving and restoring the natural purification systems, not the least of which is that nature does for free what would cost a fortune to do artificially. These same reasons apply to avoiding water contamination as much as possible. After all, cleaning water is generally more costly than avoiding polluting it. For example, keeping feces contaminated runoff from agriculture out of the water supply is certainly cheaper than removing the contamination.