Projecte de

Ponds for biodiversity

The goal of this project is the restoration of pond habitats in the Girona region, in order to help biodiversity,  especially amphibians such as the Spadefoot toad (Pelobates cultripes). The population of this species has decreased steeply. Freshwater ecosystems in this area rare suffering degradation, and thus, projects such as this one, are very necessary.

Species found during the surveys in May 2020: Spadefoot toad, stickleback, Mediterranean tree frog, water snake


With the funding and technical support of Andrena, La Sorellona created a new temporary pond in former farmlands, and has improved the ecological conditions of the pond at Can Rufí.

The Bassa de Can Rufí was in a turbid state, due to the abundance of invasive fish and exotic turtles. The pond was emptied, anoxic sediment was dredged, and fish and turtles were removed.

This pond is gradually recovering; its transparency has increased a lot, and in it breed many dragonflies, macroinvertebrates, and amphibians. This pond participates in the project ESCANYAGATS, which aims to secure populations of stickleback, a fish that is regionally threatened by climate change and river pollution.

With this restorations, connectivity with other freshwater habitats has increased, improving the possibility of metapopulations.


Turbid water / Clear water


Green turbidity is the result of phytoplankton proliferation in the water, causing an algal bloom. This is a function of the nutrient status, but also due to foodweb disturbances, such as the abundance of species that prey upon  herbivorous zooplankton, and that can stir the sediment, sending extra nutrients to the water column.

The current condition of an ecological system is its state. Because , it is possible for them to occupy more than one state for a given set of environmental conditions. This is the foundation of the ecological theory of  ALTERNATIVE STABLE STATES.

Shallow lakes can have two different states: a clear state, dominated by aquatic vegetation, and a turbid state, dominated by a high algal biomass.  Sometimes, biomanipulation is needed, in order to recover the clear state in an ecosystem. See Marten Scheffer et al. Alternative equilibria in shallow lakes

Invasive fish and turtles can alter strongly freshwater ecosystems. An excessive population of domestic ducks can decrease water quality, too.

Bassa de Can Rufí, abans i després de la restauració


In order to preserve the quality of our lakes and ponds, please DON’T introduce any animals in them: fishes, crabs, turtles…

La Sorellona

La Sorellona is an association that specializes in environmental education and volunteering programs. It organizes Summer camps with a focus on nature and outdoors activities.