Threats to biodiversity and naturalness

The threats to biodiversity can be divided into two groups: one that results from human action outside the delta area, and the other due to unsustainable human action within the delta.

3.1. WATER QUANTITY

Humans have modified the river discharge to the Delta, mainly by hydro-technical works, particularly dams, in upstream river sections. Such interventions were generally considered the most important threat recorded. These changes affect many aspects of the functioning of the Delta, but are particularly important for migratory fish species, and also flora and fauna that depend on specific flooding patterns.

Increased drainage intensity and decreased water storage in the catchment cause increased amplitude and a shortened duration of floods. Storage lakes for hydropower production cause a leveling-off of the flooding régime in the Delta, especially of the minor floods outside the main flood season (Compania Nationala "Apele Romane", 2006).

3.2. SEDIMENT SUPPLY

Regulation of the upstream sections of a river tends to reduce the sediment transported to the delta. Most of the bedload and part of the suspended sediment are trapped in storage lakes. Sediment transported to the Danube Delta was reduced by about 30% in past decades by the construction of the Iron Gates Dam on the Danube and by numerous minor dams at the apex of the Delta.

3.3. SEA LEVEL RISE

Not only the upstream conditions influence the development of deltas -downstream conditions such as sea level rise have an influence as well. In fact, a relative rise in the sea level is a precondition for the development of a delta at a river mouth. But a rapid acceleration in the rise of sea level increased the wave action, causing erosion on the Delta's marine margin. That is why the very famous and profitable beaches of the Romanian Black Sea coast have narrowed over the last 2 decades, affecting the ecological equilibrium.

The Biosphere Reserve's Black Sea coastline, with a length of almost 200 km, is currently affected by an intensive and continuous degradation caused by marine erosion. The shoreline is shrinking at an annual rate varying from a few meters to 15-20 m for the coastline of the Delta between Sulina and Cap Midia, and around 0.2-0.5 m for the coastline with sea cliffs south of Constanta.

Erosion along the coastline is both natural and man-made. From among the human activities of great impact on the coastline one may mention the hydro-technical works on the Danube and its main tributaries, the ports, and coastal engineering works. The hydro-technical changes performed on the Danube and its main tributary have caused a fall in the input of sediments to the coastal area by over 50%, as compared to the values registered before the building of the dykes. Thus, a great sedimentary imbalance has been created in the coastal zone, which has in turn initiated the erosion process. The port facilities and other coastal engineering works, such as the protection dykes for the Sulina navigation channel, the breakwater piers of the Midia, South Constanta and Mangalia ports, and the coastline protection works on the tourist beaches, also cause major environmental imbalance along the littoral.

Concerning these tendencies, I should say that considering global climatic changes and the general rise in the sea level, as well as the regional geo-ecological conditions that characterise the Danube - Danube Delta -Black Sea geo-system, one can estimate that the medium-term erosion process will be at least as active as in the past 2 decades. The long-term predictions reveal an extension of beach erosion, especially because of the continuous decrease of sand material in the coastal area, because of the persistent rise in sea level and the increasing energy level of the hydro-meteorological factors - storms.

Many countries consider the problem of losing land by erosion of their coastline to be of national importance. Beach erosion leads to territory loss, but it especially affects the tourist industry, causing significant losses to national economies. The process of erosion also disturbs the ecological state of the coastal area almost irreversibly.

3.4. CHANGES IN THE LAND USE

One of the greatest threats to the biodiversity and naturalness of the Danube Delta Biosphere Reserve has been the appropriating of natural areas for other purposes, principally for agriculture, industrial zones, forestry, fish farms etc. The area of natural habitat, particularly wetlands, in the Delta has been greatly reduced in the past. Forty five percent of the Delta remains as natural habitat, mainly due to strict protection of the scientifically interesting areas. Now, I can express optimism that the international designation of the Delta under the Ramsar Convention and European Directives will reduce the risk of further losses.

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