Human population has increased at a phenomenal 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.)

Future changes in global changes (for example, from climate change), could perturb many systems that humans rely on, such as:

Collapsing Fisheries
Still some use of wild food use in the modern world. Specialty foods (fungus, some plants, game/bushmeat) are part of this, but the most important are fisheries. All wildfood sources would be threatened any way, due to increasing human population and technology. But climate change is affecting the abundance and distribution of much of wildlife.

Increasing human populations, environmental changes to the seas, and advances in fishing technology has caused the collapse of many once-productive fisheries. Humans have had to start "fishing down the food chain" (going after smaller-bodied species because the larger ones are no longer abundant enough to be economical.)

From Andrew's ENVR 2000 Blog

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. After a relatively short period of time, farming will exhaust the nitrogen in the soil (part of the reason the Fertile Crescent isn't so fertile any more, and why in just a few hundred years of agriculture the Native Americans of the Northeast had to plant crops with fish). In older societies natural sources of nitrogen were used (dead fish; 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 agricultural use, increasing yields such that where one acre used to support 1.9 people it now supports 4.3. Unfortunately, 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 beneficially 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).

The Green Revolution: name given to mid-20th Century international programs to develop new strains of crops (esp. rice) and new breeding and planting strategies to feed the developing world (esp. Asia). Brought industrialized farming techniques (including extensive use of nitrogenous fertilizers; petroleum powered farm equipment; etc.) to developing nations. On the one hand, it ended mega-death (1 million or more fatalities) famines that used to hit greater India, southeast Asia, China, etc., during earlier periods. On the other hand, it resulted in biodiversity and soil loss, increased air pollution (including GHGs), decreased water availability and quality, dangerous population increases, and decreased quality of human health in some of these regions.

As climates change, there will be changes in the timing and distribution of crops and other domesticated species and their pollinators (which might not match up). Also, the new zones into which they move may not have the appropriate soils or growing seasons, so harvests might decrease. Furthermore, changes in precipitation may be unfavorable for some crops and regions. Finally, increased CO2 levels may not be good for all plant species: in particular, grains and related grasses evolved in the context of (and grow better in) low CO2 atmospheres.

An Historic Case of Food Crises: The Irish Potato Famine
People don't expect the unexpected and they hang onto institutional practices.

What are the prospects of a human boom-and-crash-cycle based on the collapse of food resources? We've seen examples in the past of civilizations that catastrophically fail due to institutions that render their people and environment incapable of supporting them.

- but there is something distancing about these remote pre-industrial societies.

Consider an industrial-age example:

  • The Irish Potato Famine (1845-1851): A perfect storm of rational people following their self-interest in a land governed by institutions that couldn't adapt to a novel threat.

    Now IMAGINE a similar blight today, only:

    Public Health and Climate Change
    Improvements in the general public health are the main means to reduce disease in any population. This works on the principle that "an ounce of prevention is better than a pound of cure". Thus, such things as clean drinking water; sanitary disposal of sewage, waste water, and other waste; healthy diets; access to preventive medicine and first aid; and (when necessary) access to more extreme medical care (hospitalization, onsite treatment of infectious illness, etc.) can greatly reduce the spread of disease.

    Thermal stress itself can be a cause of health problem. The European heatwave of August 2003 saw an increase in fatalities in a highly-industrialized country. As such heat waves become more frequent, they might produced increased levels of mortality (esp. in poor nations). Even in industrialized nations, increased energy draw for greater use of air conditioning will produce more energy use, leading to more greenhouse gases, leading to more heating...

    Image from Vandentorren et al. 2004 (A. J. Publ. Health 94:1518-1520.)

    Changed availability of food will affect public health as well, as will migration of disease vector organisms (mosquitos, etc.) into regions they did not formerly inhabit. Furthermore, increased biological stressors (thirst, hunger, etc.) makes people more vulnerable to endemic disease, and when whole communities are under such stress, this can lead to epidemics.

    Overall, like so many things, these public health effects of climate change will disproportionately affect poor (mostly equatorial) nations.

    Abrupt Climate Change
    The Holocene (the last 11,700 years) has been a period of relative climate stability, compared to 9K fluctuations over the earlier Pleistocene Epoch. All our our agriculture, water use, etc., were developed in this context of Holocene stability.

    However, climate change does not always affect the world gradually. As we have seen there are many cases of "tipping points"/"phase transitions" in Earth systems: not all environmental changes happen as gradual steps, and indeed many can change very dramatically very quickly.

    Since the early 1980s paleoclimatologists like Wally Broecker and James Hansen have recognized that the Earth is subject to abrupt climate change: that the Earth system switches from one climate regime to another in just a few years. (Inertia, however, means that it takes a longer time before the full effects of the transition are felt, but the operating system itself flips from one to another very quickly.) At present, there are three major aspects of abrupt climate change which are of paramount concern: