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Negative effects of land reclamation

SpausdintiPrint

Land reclamation in the wetlands of the Žuvintas biosphere reserve resulted in a number of negative consequences:

Land abandonment
Part of drained land appeared to be not suitable for intensive agriculture or forestry and currently is abandoned and overgrown by trees and bushes.
Maintenance costs
Maintenance of the drainage system and endikements in the peaty soils requires substantial resources. That makes maintaining certain drained areas not only ecologically,  but also economically unfeasible.
Soil erosion
Peat mineralizes and shrinks fast when it is dried and exposed to air. 1cm to 5cm of peat layer can be lost per year depending of conditions. It's calculated that approximately 1 m of peat layer is already lost since the drainage was established in Amalvas mire.
Input to climate change
Peat mineralization process also results in increased emissions of greenhouse gasses (mainly CO2 and N2O). According to preliminary calculations ~15 thousands tones of carbon dioxide is annually produced in drained Amalvas peatlands.
Fire
Fire, sometimes very severe (in 1983, 2002), appears occasionally in the degraded bog area and cause additional damage to the bog.
Impact on biodiversity
Hydrological alterations caused degradation of all the former Amalvas active raised bog and part of bog woodlands (~1600 ha). Approximately 1200 ha area of the habitat still is capable to regenerate. Currently overgrowth by trees takes place and reduction of open areas required by such species like Black grouse, Golden plover, Curlew, Wood Sandpiper.
Changes in Zuvintas mire are not so radical. Increase in tree growth is registered to be up to 8% at a distance of ~200 m from the ditches, but the effect of superficial drainage is broader. Patches of raised bog communities start appearing at a distance of 200-400 m and become typical at ~500 m from the ditches.
The sluice-gates built on the outlets of Žuvintas and Amalvas lakes changed hydrodynamics of the lakes. Average yearly water level was lowered by 17 cm in the Žuvintas Lake and water level fluctuation decreased from 1.2 m to only 0.7 m. This negatively influenced not only the lake (habitat 3140 is in unfavourable status due to increased sedimentation process) with surrounding alluvial meadows, but also hydrologically bound mires.
During last 24 years there was observed constant reduction (~150 ha) in the open raised bog area due to encroachment by trees. Quantitative and qualitative changes of moss layer structure are observed.
3140 Hard oligo-mesotrophic waters with benthic vegetation of Chara spp. is in unfavourable condition. The area covered by Chara spp. is shrinking, what in turn decrease the feeding source for the waterfowl. The shrinking of the open lake area speeded up.
Changes in habitats affected species. Open raised bog species significantly reduced in number. For example, Wood Sandpiper Tringa glareola more than 2 times comparing to 1966; Curlew Numenius arquata - 8 times as compared to 1966; Numbers of breeding ducks in the lake significantly reduced.

 

© 2009 „WETLIFE“ LIFE07 NAT/LT/530 .

sprendimas: IMODUS