Understanding ecosystem service interactions in agricultural landscapes: The importance of land-use legacies

Background/Question/Methods

Agriculture is a key driver of change in the Anthropocene. Feeding the world and driving the transgression of several planetary boundaries, agriculture is both a critical factor for human wellbeing as well as a major driver of environmental decline. As the human population expands to approximately 10 billion people, we will be compelled to find a way to adequately feed this population while simultaneously decreasing the environmental impact of agriculture, even as global change is creating new disturbances to which agriculture must respond. This predicament demands better understanding of the impacts of agriculture across spatial and temporal scales. Global solutions must take into account the day-to-day realities of farmers and local solutions must scale up appropriately to form global solutions. At the same time, local history also plays a role determining the outcome of today’s actions, and should therefore be taken into consideration.

Results/Conclusions

While we often ignore cross-scale effects, the reality is that they can have a massive impact on our efforts to reduce the environmental impacts of agriculture. For example, understanding patterns of agricultural fertilizer use from one hundred years ago can improve water quality management today. Hundred-year cumulative phosphorus (P) budgets show a strong linear relationship to average soil P content in the St. Lawrence River sub-basin. Because soil P levels play a key role in determining today’s runoff, the implication is that paying attention to the history of fertilizer is key to controlling eutrophication today. Our meta-analysis of data on soil labile and total P content after agricultural abandonment in 94 published studies shows a potentially large and enduring legacy of past agriculture: soil P content was typically elevated after abandonment compared to reference levels, but reduced compared to soils that remained under agriculture. These effects can last a long time: the most intense soil P elevation occurred 30-50 years after abandonment; for P-depleted areas, effect can be up to 100 years long. Thus, we must keep in mind a very long time frame for managing some environmental effects of agriculture. Cross-scale effects through space and time can have important outcomes for agriculture and the environment. Knowing, and considering, the history of agricultural landscapes, can improve today’s management decisions.