Botkin Environmental Science Earth as Living Planet 8th txtbk

11.1 An Ecological Perspective on Agriculture 213
Africa leading the list with 21 nations. In the Republic
of the Congo, three-quarters of the population is
undernourished, and in 25 nations at least one-third
of the population is undernourished, according to the
UNFAO (Figure 11.2). 6
Suddenly, people of the world need a great increase in
food production, in part because of the expanding human
population, in part because of competition between crops
for food and crops for fuel, and in part because of droughts,
floods, and other environmental impacts that have decreased
agricultural production. What can be done to meet the
world’s growing need for food and, second to that, its need
for fuel? Can agricultural production increase? By how much?
And at what costs, environmental and economic?
11.1 An Ecological
Perspective on Agriculture
Farming creates novel ecological conditions, referred to
as agroecosystems. Agroecosystems differ from natural
ecosystems in six ways (Figure 11.3).
Ecological succession is halted to keep the agroecosystem
in an early-successional state (see Chapter 5).
Most crops are early-successional species, which means
that they grow fast, spread their seeds widely and rapidly,
and do best when sunlight, water, and chemical nutrients
in the soil are abundant. Under natural conditions, crop
species would eventually be replaced by later-successional
Pre-agricultural ecosystem
Agroecosystem
FIGURE 11.3 How farming changes an ecosystem. It converts complex ecosystems of high structural
and species diversity to a monoculture of uniform structure, and greatly modifies the soil. See text for
additional information about the agricultural effects on ecosystems.