Agriculture: Re-adaptation to the Environment

Agriculture—since its beginnings approximately 10,000 years ago—has significantly modified natural ecosystems in order to yield adequate and permanent staple food supplies for human populations. In creating artificial ecosystems, agriculture inherently interacts closely with pre-existing environmental conditions. Hydrology, soils, climate, topography and biology all have a major influence over the productivity and profitability of agriculture. Traditional agriculture has worked with these inter-relationships with the environment by adapting in ways that coordinate with local ecology. As early as 200 BC, Roman farmers were aware of methods to manage soil fertility. For example, Cato the Censor advised that land should be allowed to lie fallow for a year, as well as planting various legumes “not so much for the immediate return as with a view to the year later”.1 The Romans were not alone in the observation of lost soil fertility. In the same period, Chinese were using “green manure, ” a legume crop plowed into the ground before the next planting.2 While the recognition of the relationship between agriculture and the environment is longstanding, concern continues to heighten over increasing agricultural pressures on the environment. This is particularly true for aquatic and riparian habitats, as well as wetland ecosystems. Irrigated agriculture underwent exponential growth over the past half century—from 50 million hectares globally in 1900 to 267 million hectares in 2000.3 As seen in figure 1, water use—dominated by irrigation—saw a parallel rate of growth. The marked increase in irrigated area from th