In wetland environments, vegetation has an important role in ecological functioning. The main goal of this work was to identify an optimal combination of Sentinel-1 (S1), Sentinel-2 (S2), and Pleiades data using ground-reference data to accurately map wetland macrophytes in the Danube Delta. We tested several combinations of optical and Synthetic Aperture Radar (SAR) data rigorously at two levels. First, in order to reduce the confusion between reed (Phragmites australis (Cav.) Trin. ex Steud.) and other macrophyte communities, a time series analysis of S1 data was performed. The potential of S1 for detection of compact reed on plaur, compact reed on plaur/reed cut, open reed on plaur, pure reed, and reed on salinized soil was evaluated through time series of backscatter coefficient and coherence ratio images, calculated mainly according to the phenology of the reed. The analysis of backscattering coefficients allowed separation of reed classes that strongly overlapped. The coherence coefficient showed that C-band SAR repeat pass interferometric coherence for cut reed detection is feasible. In the second section, random forest (RF) classification was applied to the S2, Pleiades, and S1 data and in situ observations to discriminate and map reed against other aquatic macrophytes (submerged aquatic vegetation (SAV), emergent macrophytes, some floating broad-leaved and floating vegetation of delta lakes). In addition, different optical indices were included in the RF. A total of 67 classification models were made in several sensor combinations with two series of validation samples (with the reed and without reed) using both a simple and more detailed classification schema. The results showed that reed is completely discriminable compared to other macrophyte communities with all sensor combinations. In all combinations, the model-based producer’s accuracy (PA) and user’s accuracy (UA) for reed with both nomenclatures were over 90%. The diverse combinations of sensors were valuable for improving the overall classification accuracy of all of the communities of aquatic macrophytes except Myriophyllum spicatum L.

How can the governance of nature areas foster the sustainability of ecosystems? This is discussed with regard to larger threats on ecosystems despite larger global nature areas that reach 19 million km² of land along with larger costs per area unit. Moreover, monetization of nature with payments for ecosystem services is sometimes demanded for justification of the nature areas; however, this does not resolve the threats but faces scientific and ethical scrutiny. An alternative is the governance that incubates sustainable innovations in the nature areas for broad dissemination which generates interests in the sustainability of ecosystems. Opportunities are due to demands for ethical products, ecotourism and images of nature which generate USD 1100 billion in global markets. Sustainable innovations of using reed for insulation walls, furniture panels and upholstery in the EU can generate a few hundred million dollars in addition to present roof thatching, fodder and fuels if good functional qualities of the reed products are developed. Their functionalities can be supported by the inclusive economics, CO₂ storage, treatment of water pollution, richer biodiversity, and other ethical qualities. The governance of nature areas can prevent the present deadlock but needs the development of technical and entrepreneurial capabilities.

The authors wish to make the following corrections to this paper