The ecosystem resilience approach in wetlands

A wetland is actually the English name for 'wetland', which designates an area located on the boundary between land and water. They are often areas that are sometimes flooded and then become dry or marshy again.

In many of these areas, we increasingly see a dominance of water crassula (Crassula helmsii) and sunfish (Lepomis gibbosus). In LIFE Resilias, we show how to increase the resilience of the system, reducing that dominance.

Wetlands are mostly affected by high atmospheric nitrogen concentrations, acidification, desiccation and high inflow (influx) of nutrients from agriculture. As a result, optimal habitat for native wetland species is disappearing. These disturbances often also mean opportunities for invasive exotic species. The resilience of wetlands is further reduced as nature managers encourage fragile pioneer systems with low species densities (in both vegetation and e.g. fish populations) to facilitate species such as natterjack toads. This makes the system extra susceptible, resulting in the disappearance of native vegetation and predatory fish, while allowing them to compete with invasive exotic species such as sunfish and water crassula. Traditional action against the invasive exotic species to get them out of these wetlands is often accompanied by further damage to the native species composition. For example, the use of large equipment or pumping the pools dry which also results in the disappearance of native species. In turn, these degraded systems are precisely the ideal systems for the recovery and reintroduction of the invasive exotic species population that is often still present.

Breaking dominance and introducing native competitors
In LIFE Resilias, we increase the resilience of wetlands by breaking the dominance of exotic species and then actively encouraging and/or (re)introducing competitive or predatory native species. For example, you can supplement or restore predation pressure on sunfish by introducing predatory fish such as the native pike (Esox lucius). And water crassula can be tackled by introducing native plant species such as bank weed (Littorella uniflora) to be planted, which compete for available nutrients. This hinders dominance of water crassula.