EXTREAM (Exotic invaders in Swedish stream ecosystems: evaluation of their ecological and economic effects)

Last changed: 09 March 2020

EXTREAM aims to understand how non-indigenous species (NIS) and other global change factors jointly affect the magnitude and stability of multiple ecosystem services in streams in Sweden, and to use this information in developing economic valuation of NIS and in identification of efficient management policies

Streams and rivers support life at a most basic level by supplying fresh drinking water, and are often central to the cultural and recreational life of human societies. The provision of drinking water depends on several support services associated with waste removal and water purification, which also underlie other services, including food production. Streams constitute an important sink for excess nutrients due to high nutrient uptake rates especially by algae, and high denitrification rates.

Unfortunately, running waters may also be the most heavily degraded of the Earth’s ecosystems, as they integrate impacts of multiple stressors across catchments. Non-indigenous species (NIS) are often favoured by environmental degradation, and streams are affected by a wide variety of invaders, including pathogens.

The high upstream-downstream connectivity characterising river corridors, and strong linkages with the riparian strip, further exacerbates the susceptibility of streams to invasions. The Extream project focuses on two broad NIS groups which currently impact streams and threaten ecosystem service delivery throughout Sweden, and which are likely to pose increasing management problems in the future: invasive foundation species and pathogens. The economic part of the project examines properties of efficient management strategies of NIS in streams in Sweden. To this end a dynamic optimisation model is constructed of a selected NIS. The model rests on ecological data on the introduction and dispersal pattern of the NIS and economic data on costs and benefits from the species.


Project period
Project leader
Ing-Marie Gren
Project co-workers
George Marbuah
Project funder

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