Science for Environment Policy, issue 208: A service from the European Commission

Using a Greek case study, the system was able to identify risks from a dam construction project to species including otters, toads and tortoises.

Dams or water reservoirs have many valuable functions, supplying water for domestic and irrigation purposes, particularly in drought prone areas, and providing hydroelectric power. They can also create a milder local climate for species threatened by human activities. Nevertheless, the construction and operation of dams have social and environmental impacts, which need to be assessed in order to minimise potential damage.

The Natura 20001 network of conservation sites has been established across Europe to protect the most threatened species and habitats. This study proposed a method to evaluate and map the impact of the Akropotamos Dam, currently under construction, near a Natura 2000 site in the Pieria basin, Kavala, Greece, was used as a case study.

A four-step impact assessment and evaluation process using Geographical Information Systems (GIS) resulted in the production of maps showing areas with different impacts on threatened species. The four steps were: (1) grouping areas with similar habitats; (2) evaluating the impacts on species in each habitat area based on 10 environmental criteria and assessing the total impacts; (3) prioritising the impacts at every habitat; (4) constructing the maps which show regions with different degrees of impact.

Visualising the impacts of dam construction is a useful tool for decision-makers as priority areas for action can be clearly identified. This method can be applied to any other type of technical project which may affect nearby protected areas.

The study included the area between the Natura 2000 site and the river, where habitats and local species are likely to be similar to those protected under the Natura 2000 designation. A variety of habitat types were identified, including grasslands, forests and rocky habits and caves. These were grouped into zones, each of which experienced similar impacts from the dam project.

Among the results of the impacts of the dam on five species protected under the Natura 2000 designation, were:

• The areas nearest the river and dam site are the most susceptible, due to changes in water quality. This affects fish populations and river bank vegetation, the habitat of European otters and yellow-bellied toads.
• Increased populations in the villages along the river path during construction could restrict otters and great crested newts reaching the riverside.
• Tortoises could face problems from vegetation removal during the construction phase and increased human pressures during and after construction.
• Although yellow-bellied toads will be affected by the construction phase, the species lives in a wide variety of environments and will benefit from the abundance of water once the dam is completed. This is unlike the European otter, which will be affected by changes in water quantity and quality.

Recommendations to protect the environment for otters include: monitoring and controlling water quality, preventing sudden changes in water levels to protect the riparian vegetation and maintaining corridors between habitats.

See: ec.europa.eu

Source: Koutsos, T.M., Dimopoulos, G.C., Mamolos, A.P. (2010) Spatial evaluation model for assessing and mapping impacts on threatened species in regions adjacent to Natura 2000 sites due to dam construction. Ecological Engineering. 36:1017-1027.

Contact: mamolos@agro.auth.gr

Science for Environment Policy, issue 208: A service from the European Commission