Natural Resources: what do we use them for?
Human population has increased at a phenomonal rate over the last few centuries:
All other things being equal, if each human required the same amount of resource from the environment, we would have drastically increased that impact by population increase alone. But it is more extreme than that: modern industrial technology requires a greater draw on the natural resources per capita than a pre-industrial society. (After all, our technology uses materials such as aluminum, titanium, petroleum, and so on that are outside the scope of a non-industrial culture.)
Modern Food Production and Nitrogen:
Our direct use of wild foods has greatly decreased, at least as regards to terrestrial animals (except for game, which is limited generally to the wilderness of the developing world and sports hunters in the developed world) and plants and fungi. Fishing, however, still has a large wild-based component.
Most of our food now comes from farming. As such, it uses a substantial fraction of the planet's surface. Large scale farming to support the cities of the world necessarily requires industrial farming equipment and chemical fertilizers (in order to allow a small fraction of the population to feed the rest).
Farming allowed for a tremendous increase in population, and allows us to capture progressively more and more of the planetary biomass to feed our species. Additionally, much of energy consumption has to do with growing and transporting food stuffs.
One of the most important nutrients that farming exhausts from the soil is nitrogen. While in older societies natural sources of nitrogen were used (guano from bats and birds; sal ammoniac; etc.), the Haber-Bosch process (developed in 1908) allows us to artificially generate ammonia. Via the Haber-Bosch process, humans generate about 100 Tg of nitrogen per year for agriculatural use, increasing yields such that where one acre used to support 1.9 people it now supports 4.3. Unfoturnately, there is substantial runoff: only about 17% of the nitrogenous fertilizer is actually taken up by the crops, with the rest running into the environment.
This runoff does have some beneficialy effects, allowing wild terrestrial plants to grow more, and
thereby take up more carbon dioxide. But most of it makes its way into water systems, where it has
far more dire consequences.
Dead Zones are regions where nutrient runoff has
overfed the algae, which pulls the oxygen out of the water and kills the animals beneath:
These dead zones are found in coastal
systems around the world:
(Note that some of these include areas that were once major fisheries).
"Farming" vs. "Mining":
We can think of the way we use natural resources as either "farming" or "mining":