Two hundred years ago, citing concerns dating back to Plato and
Aristotle, English clergyman and economist Thomas Malthus argued
that population growth would inevitably outpace food productionunless
checked by moral restraint, vice, or misery. In 1960,
his concerns appeared well founded. Growing at an unprecedented
rate, the worlds population reached 3 billion, and a third
of those were undernourished.
Forty years later, the worlds population has doubled to
6 billion, but food production has grown even faster, and fewer
people are undernourished. Rising food demand led to higher input
use and improved technology and efficiency. Even so, more than
800 million peoplemostly in Asia and Africaremain undernourished.
For many of these people, secure and sustainable access to sufficient
food for active, healthy livesfood securitydepends
on income from agriculture, and thus on the productivity of agricultural
land and labor.
World-average cereal yields rose by more than 2 percent per year
during the 1960s and 1970s, driven by the improved seed varieties
and increased input use of the Green Revolution. However, yield
growth has slowed since then and the Food and Agriculture Organization
(FAO) projects that cereal yield growth will slow to a global average
of 0.8 percent per year over the next three decades. Do soil erosion,
soil fertility depletion, and other forms of land degradation threaten
the productivity gains achieved in the past? Could Malthus be right
after all?
Because relevant data are scarce, the extent to which
yields have been reduced by land degradation has been difficult
to determine.
Recent analysis by ERS economists, in collaboration with soil scientists
at USDAs Natural Resources Conservation Service and Ohio
State University, finds that yield losses to soil erosion vary
widely by crop and region, but average 0.3 percent per year worldwide
when farmers practices are held constant. Given FAOs
projections of slower yield growth, further yield losses of this
magnitude could reverse recent reductions in the number of people
who are food insecure. However, farmers practices do change
over time in response to changing conditions, so actual yield losses
to land degradation are typically lower. For example, ERS analysis
finds that yield losses to soil erosion in the North-Central U.S.
are less than 0.1 percent per year when farmers choose management
practices that are most profitable over the long term.
ERS research
suggests that land degradation does not threaten food security
at a global scale, but impacts vary by location.
Yield losses due to land degradation do pose problems in areas
where soils are shallow, fields are steeply sloped, property
rights are insecure, and farmers have limited access to inputs,
information,
and markets. Any further slowing of yield growth in the future
would increase the importance of measures to address these challenges.