Alpine rivers hold important clues for preserving biodiversity and coping with clim...( Marginal plants particularly trees p...)

Marginal plants, particularly trees, play a crucial role in sustaining the biodiversity of Europe's big river systems, according to a recently held workshop organised by the European Science Foundation (ESF). This finding provides important clues for protecting Europe's rivers against a combined onslaught from human development and climate change, which are tampering with existing ecosystems and changing both the physical and biological forces acting upon them.

Both aquatic plants (living in rivers) and, more importantly, riparian ones (growing along the banks and on islands) play critical roles in building and sustaining habitats for colonisation by other species, and in the chemical and biochemical processes that keep rivers and their ecosystems healthy, according to Professor Angela Gurnell, convenor of the ESF workshop and director of the Centre for Environmental Assessment, Management and Policy at King's College, London.

Gurnell described some plant species as "ecosystem engineers" marshalling habitat development and maintenance. Furthermore, ecosystem engineering by plants operates at many different spatial scales, and in different ways along rivers from their source to mouth. But the vegetation itself is part of the habitat it supports and so vulnerable to the same forces, with the potential for tipping whole ecosystems into new states when certain thresholds are breached, for example as a result of a slight change in climate or river flows.

"Vegetationphysical process interactions are highly complex and are subject to distinct thresholds across which massive shifts in system condition can occur," said Gurnell. "Threshold crossing can be driven by both physical and biological processes and is particularly susceptible to changes in climate, river flow and channel management."

The ESF workshop focused on Alpine systems because most of Europe's largest rivers, including the Rhine, Rhone and Danube have their source in
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