549
source thus shifts towards the upper part of the canopy, where the large, raised reed
leaves enhance rather than reduce signal backscattering. An important observation
concerns the temporal evolution of backscattering. We noted that the backscattering
peak is reached when consistent backscattering mechanisms are in place (in May/
June), correlating with the increased aerial biomass.
The foregoing observations show that there is a transition from surface backscattering in early spring, during which the first plant growth phase occurs (May–June),
to dipolar or double-bounce non-dominant backscattering. This mechanism continues to be dominant during the second phase (July–August) up to plant maturity; it
then turns into volume backscattering during the senescence phase.
On VH polarization, the species of the various reed classes make up a very
homogeneous group, and there are few differences between the various seasonal
signatures. For these classes, the backscattered power peak is reached in May and
June, when consistent backscattering mechanisms are in place and the aerial biomass reaches its peak height.
17.8 Conclusion
According to research conducted by the United Nations Environment Programme,
40% of the global economy depends on the proper functioning of ecosystems. In
most cases, the ecosystem that needs restoring has been degraded, damaged, transformed or completely destroyed as a direct or indirect result of human actions.
Ecological restoration should become a priority so as to limit the process of degradation of the environment, to contribute to the preservation of fragile habitats and of
critically endangered species and to ensure the valorization of natural resources.
Over time, human intervention has manifested itself in more than a quarter of the
entire surface of the Danube. This intervention was brutal and has rendered ecosystem restoration very difficult. Over time, the development of fluvial-maritime navigation and of resource use policies applying to the Danube Delta (fish, agricultural,
forestry, and other resources) has determined the main water system and landscape
transformations in the Danube Delta.
After the fall of the communist regime, ecologic restoration actions were conducted in the delta. This ecologic reconstruction policy concerns all the dammed
areas (27.6% of the current surface area of the delta) that had been previously developed for agriculture, fish farming and reed processing. Considering that the Danube
Delta includes 30 types of ecosystems that are highly dependent on river level oscillation, the main objective of this ecological recovery is to restore the natural hydrological circuit of the economically developed areas. A solution to these efforts of
reconnection to the hydrological regime of the delta was suggested in 1994; it consisted of digging holes in the dykes to allow the water to enter and flow freely in
these dammed areas. For the observation and analysis of the restored ecosystems in
these areas, we relied on state-of-the-art Sentinel-1 and Sentinel-2 radar and optical
17 Alteration and Remediation of Coastal Wetland Ecosystems in the Danube Delta…
source thus shifts towards the upper part of the canopy, where the large, raised reed
leaves enhance rather than reduce signal backscattering. An important observation
concerns the temporal evolution of backscattering. We noted that the backscattering
peak is reached when consistent backscattering mechanisms are in place (in May/
June), correlating with the increased aerial biomass.
The foregoing observations show that there is a transition from surface backscattering in early spring, during which the first plant growth phase occurs (May–June),
to dipolar or double-bounce non-dominant backscattering. This mechanism continues to be dominant during the second phase (July–August) up to plant maturity; it
then turns into volume backscattering during the senescence phase.
On VH polarization, the species of the various reed classes make up a very
homogeneous group, and there are few differences between the various seasonal
signatures. For these classes, the backscattered power peak is reached in May and
June, when consistent backscattering mechanisms are in place and the aerial biomass reaches its peak height.
17.8 Conclusion
According to research conducted by the United Nations Environment Programme,
40% of the global economy depends on the proper functioning of ecosystems. In
most cases, the ecosystem that needs restoring has been degraded, damaged, transformed or completely destroyed as a direct or indirect result of human actions.
Ecological restoration should become a priority so as to limit the process of degradation of the environment, to contribute to the preservation of fragile habitats and of
critically endangered species and to ensure the valorization of natural resources.
Over time, human intervention has manifested itself in more than a quarter of the
entire surface of the Danube. This intervention was brutal and has rendered ecosystem restoration very difficult. Over time, the development of fluvial-maritime navigation and of resource use policies applying to the Danube Delta (fish, agricultural,
forestry, and other resources) has determined the main water system and landscape
transformations in the Danube Delta.
After the fall of the communist regime, ecologic restoration actions were conducted in the delta. This ecologic reconstruction policy concerns all the dammed
areas (27.6% of the current surface area of the delta) that had been previously developed for agriculture, fish farming and reed processing. Considering that the Danube
Delta includes 30 types of ecosystems that are highly dependent on river level oscillation, the main objective of this ecological recovery is to restore the natural hydrological circuit of the economically developed areas. A solution to these efforts of
reconnection to the hydrological regime of the delta was suggested in 1994; it consisted of digging holes in the dykes to allow the water to enter and flow freely in
these dammed areas. For the observation and analysis of the restored ecosystems in
these areas, we relied on state-of-the-art Sentinel-1 and Sentinel-2 radar and optical
17 Alteration and Remediation of Coastal Wetland Ecosystems in the Danube Delta…