Once, most of the world's vegetation consisted of perennial plants.
Agriculture has largely replaced them with annual crops, which have
to be replanted each year.
Since about 2000, scientists have
been able to realize the dream of developing perennial versions
of food plants such as maize, wheat, and legumes. Perennials have
deeper roots, which prevent erosion and hold onto more minerals
from the soil, so that they need less fertilizer and water. They
do not need tilling, so the soil instead of exhaling carbon becomes
a carbon sink. Yields could be greatly increased in some of the
world's poorest regions.
Farmers in Malawi are already
getting radically higher yields by planting rows of perennial pigeon
peas between rows of their usual staple, corn. The peas are a much
needed source of protein for subsistence farmers, but the legumes
also increase soil water retention and double soil carbon and nitrogen
content without reducing the yield of the primary crop on a given
plot of land. . . . [it has been calculated
that] replacing 2 percent of the world's annual crops with perennials
each year could remove enough carbon to halt the increase in atmospheric
carbon dioxide. Converting all of the planet's farmland to perennials
would sequester the equivalent of 118 parts per million of carbon
dioxide enough, in other words, to pull the concentration
of atmospheric greenhouse gases back to preindustrial levels.
(Scientific American, Dec. 2011.)
More research is needed to bring this
to the scale of conventional crops, and it will probably take another