Agriculture Reference
In-Depth Information
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Greater reliance on bioenergy will further intensify competition for water,
soil nutrients, and land and will increase the amount of water used in agri-
culture. Some estimates suggest that by 2050, the amount of water depleted
for biofuel production may be similar to what is used today for all of agri-
culture (Comprehensive Assessment 2007). Nutrient depletion by biofuel
crops will also need to be balanced by nutrient additions as otherwise crop
productivity is likely to decline over time.
There are numerous areas for research on biofuels: how to best produce them from
sources other than cereals, their consequences for water use, their role in slowing
climate change, and their relative advantage when compared to alternative sources
of energy like solar, wind, geothermal, and tidal. The question of biofuels is further
analyzed in Chapter 17.
loss of ecosystem seRvIces
A final threat to sustainable food production is the loss of ecosystem services. An
eco-
system
is defined as a dynamic complex of plant, animal, and microorganism com-
munities and the nonliving environment interacting as a functional unit (Millennium
Ecosystem Assessment [MEA] 2005).
Ecosystem services
are the benefits people
obtain from ecosystems. These benefits include food, water, disease management,
climate regulation, spiritual fulfillment, and aesthetic enjoyment. The concept of
ecosystem services, then, brings together the discussion in other sections on food
needs, water scarcity, land degradation, and climate change, while integrating these
with many other factors. Humans are fundamentally dependent on the flow of eco-
system services.
The MEA (2005) found that over the past few decades, humans have had a greater
impact on ecosystems than at any other time in history. People have been success-
ful in meeting rapidly growing demands for food, freshwater, timber, fiber, and fuel
but at the cost of many other ecosystem services. A full 60% of ecosystem services
examined were found to be subject to degradation or unsustainable use. Of special
concern are services relating to freshwater, capture fisheries, air and water purifica-
tion, and the regulation of regional and local climate, natural hazards, and pests.
There has also been a substantial and largely irreversible loss in the diversity of life
on Earth. Among other things, the MEA found that during the past few decades:
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More land was converted to cropland than was done in the preceding 150
years.
Approximately 20% of the world's coral reefs and 35% of its mangrove area
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were lost.
More water is held in reservoirs than in natural rivers because of dam
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construction.
Flows of nitrogen in terrestrial ecosystems have doubled.
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Across taxonomic groups, the population size or range of most species is
declining.
