PREWET: Minimizing negative impacts of peatland rewetting on stream primary production and algal biodiversity

Following EU regulation, Sweden has budgeted 765 million SEK for rewetting previously ditched peatlands to restore biodiversity, decrease greenhouse gas emissions and enhance water quality.

Yet, so far, rewetting of boreal peatlands has resulted in increases in water color (‘brownification’), decreased pH levels, and elevated organic nutrient exports.

Such changes could have unwanted consequences for fundamental ecosystem processes downstream of restored peatlands and thereby counteract goals of the restoration, although this remains untested.

Therefore, I will determine how peatland rewetting and brownification affects key aquatic ecosystem processes by comparing metabolic rates, algal biomass, and diversity in streams draining pristine, ditched, and rewetted peatlands across Sweden and Finland.

I will also use an outdoor mesocosm experiment and laboratory experiments to directly assess the impact of brownification on stream metabolism and algae under controlled conditions to decipher the links between browning, stream metabolic activity, and greenhouse gas production.

My project aims to establish a landscape model for identifying potential rewetting sites that improves the balance of environmental cost and benefit, and to deliver mechanistic understanding of relationships between organic matter loading and stream metabolism that will be applicable across boreal ecosystems, where browning due to restoration, climate change, and intensive land-use practices is widespread.