COS 101-2 - Agricultural ditches: Finding the balance with ecosystem service provisioning in intensive working landscapes

Background/Question/Methods

Suitably managed, ditches and riparian edges represent biodiversity hotspots within increasingly homogenous and depauperate agroecosystems, hosting rich communities of plants, macroinvertebrates, fish and riparian wildlife. With agricultural intensification and extensification increasing and climate change modifying agroecosystems globally, it is imperative that agro-landscapes are carefully managed to minimize degradation of ecosystem functioning and thus avoid loss of critical ecosystem services. Agricultural water extraction, storage behind dams, diversions, dredging and clearing of riparian vegetation can impact more naturalized flow regimes. Through a systematized literature review encompassing 39 peer reviewed papers and ongoing field observations at study sites in the South Nation watershed, ON, we explore how ecologically significant aspects of low flow affect aquatic ecosystem functions. We then consider how agricultural management practices create and interact with these conditions in human-made drainage/ irrigation ditch systems, and how this may be exacerbated under climate change with agricultural expansion and intensification.

Results/Conclusions

While low flows can be beneficial, or even necessary for some biotic processes, further reductions in flow antecedent conditions was found to negatively impact ecosystem functions. These effects can be separated into direct and indirect effects, and can be driven by management practices in agricultural drainage systems. For example, dredging and removal or riparian vegetation directly impacts water purification through agrochemical emissions, and indirectly through sediment accumulation influencing pollutant retention. The consequences for provisioning of ecosystem services in agricultural drainage ditches are likely to grow in importance as agriculture expands and intensifies in Canada under climate change. To explore these concepts further, we highlight a case study of an agriculturally-dominated watershed that is the focus of the Environmental Change Onehealth Observatory (ECO²), a Government of Canada Federal interdepartmental project to study the consequences of loss of natural capital and associated ecosystem services for: 1. Biodiversity; 2.[Re]emergence of zoonotic diseases of importance to human health; and 3.[Re]emergence of infectious diseases of importance to livestock health, with the aim to find a balance between providing food and other commodities which support the well-being of Canadians with the need to provide increased biosphere stewardship.