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International audience; Sustainable management of mangroves depends on our ability to maintain ecosystem functions. It requires a careful monitoring of several forest characteristics such as the species composition. Very high resolution multispectral satellite images provide pivotal information at the individual tree scale that may support identification and mapping of species of mangrove trees emerging at the canopy level. In this study, we showed that fine scale spectral responses of four common Asian mangroves species were and remained distinct over one decade and, independently of both the satellite sensors and the angular configurations of image acquisitions. We began an important radiative transfer modeling work to interpretation such promising observations

International audience; There is a need to document how fast mangrove coasts are changing. Within the framework of the INDESO project, we are implementing methods for monitoring changes in Indonesian mangroves over the past decade. The Perancak river estuary, Jembrana, Bali was selected as a pilot site to analyze the impact of aquaculture and plantation practices in a 7 km² mangrove area. During the 80’s, most of the mangrove forest was converted to shrimp ponds. However many of shrimp ponds have been abandoned since the 90’s and covered by mangroves through plantation programs. We based our analysis on a temporal series of VHR satellite images acquired from 2001 to 2014 aiming to assess the vegetation change over 13 years in the study site. We mapped and quantified the trends of evolution in mangroves in terms of surface extents, forest types and forest structure (young, adult, mature). Our results showed that the Perancak estuary is undergoing the greening, i.e. increasing extent and continuous growing of mangroves. With this approach, we proved that both sustainable and unsustainable coastal zone management practices such as mangrove deforestation, plantation or protection, can be identified and mapped from VHR satellite images

Mangroves are important ecosystems that provide a huge range of benefits for coastal communities. The management of mangroves requires multiple methods and approaches that contribute to answering the policy relevant questions. Our site is in the Perancak estuary, Bali, where mangroves were degrading in 1980's due to the conversion of mangrove forests to aquaculture ponds and later reestablished in early 2000 when many aquaculture ponds were abandoned due to economic crisis and the diseases. Monitoring of mangroves in this area has been conducted since 2004, aiming to identify the ecological processes in mangrove ecosystems that support mangrove conservation initiatives and coastal management. The study showed the recovery in net primary productivity (NPP) and carbon sequestration capacity of mangroves in abandoned ponds. Our results support the view that mangroves are highly productive ecosystems that can recover from disturbances even from extensive land conversion through destruction of mangrove trees, and undertake reshaping of hydro-biogeochemical processes. Mangrove extent can grow by self-regeneration and replantation throughout the 7.5 km² estuary, this resulting in the reverse process of aquaculture site conversion into mangroves areas. In the frame of the INDESO project (Infrastructure Development for Space Oceanography) mangrove changes in this region are monitored in support of a series of very high resolution satellite images acquired since 2001. The analysis of these data supports the definition of keystone regions for monitoring biodiversity recovery and ecosystem protection. Our goal is to provide recommendations for sustainable management of mangrove coasts that are understandable to local government and stakeholders, including the recommendation that supports the establishment of Regional Marine Conservation Area (or Kawasan Konservasi Laut Daerah, KKLD) of the Perancak estuary.

There is a need to document how fast mangrove coasts are changing. Within the framework of the INDESO project, we are implementing methods for monitoring changes in Indonesian mangroves over the past decade. The Perancak river estuary, Jembrana, Bali was selected as a pilot site to analyze the impact of aquaculture and plantation practices in a 7 km² mangrove area. During the 80’s, most of the mangrove forest was converted to shrimp ponds. However many of shrimp ponds have been abandoned since the 90’s and covered by mangroves through plantation programs. We based our analysis on a temporal series of VHR satellite images acquired from 2001 to 2014 aiming to assess the vegetation change over 13 years in the study site. We mapped and quantified the trends of evolution in mangroves in terms of surface extents, forest types and forest structure (young, adult, mature). Our results showed that the Perancak estuary is undergoing the greening, i.e. increasing extent and continuous growing of mangroves. With this approach, we proved that both sustainable and unsustainable coastal zone management practices such as mangrove deforestation, plantation or protection, can be identified and mapped from VHR satellite images.

Mangrove restoration has been attempted in the 7 km² Perancak Estuary, Bali since the 90's following shrimp farming loss of profitability. We characterized the surface types of estuarine zone and monitored mangrove changes since 2001 using a series of 20 very high resolution satellite images acquired over the estuary. Mangrove development was further assessed by forest inventory conducted in 2014 and diameter increment measurement using dendrometer bands installed on 83 mangrove trees in ponds and intact forests since 2011. The Perancak Estuary was cove red by over 1350 shrimp ponds accounting for 63% of the estuary area in 2014. Rhizophora planted mangroves were mostly found in the ponds whereas natural mangroves mainly established outside ponds with a clear dominance of Avicennia and Sonneratia genera. It is worth saying that, in ponds hydrologically reconnected to tidal flows due to damage dykes, natural recruitment of the two previous genera was observed. The 2001-2014 spatio-temporal analysis over the entire estuary revealed that natural mangroves have expanded from 20 to 65 ha whereas planted mangroves extent varied from 20 to 50 ha. Stretching newly mangroves in the ponds and intact areas resulted in 'greening' event in the estuary. However different characteristics of mangrove development between Rhizophora monocultures and natural mangroves were found. Sonneratia and Avicennia became dominant in the ponds as they demonstrated rapid increase in size compared to Rhizophora trees with annual mean individual tree diameter increment reaching 1.1, 0.9 cm and 0.5 cm, respectively. Even if variation in mangrove growth is observed between in the pond and intact areas, our findings proved that Avicennia and Sonneratia perform better than replanted mangroves of Rhizophora, suggesting that the adequacy of monospecies Rhizophora plantations for sustainable restoration of estuarine functions should be further questioned. (Texte intégral)

Very high resolution (VHR) satellite images provide crucial information on fast changing coastal regions of the world. Within the framework of the INDESO project, we designed a specific application dedicated to the monitoring of mangroves in Indonesia. In this work, we focused on the case study of the Perancak river estuary, Jembrana, Bali. The estuarine area was subject to aquaculture development during the 80's and most of the mangrove forest was cleared. Since the 90's, mangroves are progressively reintroduced thanks to plantation practices. Now, many shrimp ponds are abandoned. We based our analysis on a temporal series of VHR satellite images acquired since 2001 in the aim of following -up 9 years of changes occurring in mangrove vegetation. We map and quantify the trends of evolution in mangroves surface extents, forest types and structure (young, adult, mature) after ground trothing surveys. Overall, the Perancak estuary is currently greening, i.e. increasing extent and continuous growing of mangroves are observed. However, the estuarine hydrology is still constrained by ponds dykes and plantations are monocultures of Rhizophora species which are probably not the initial dominant species. The sustainability of the Perancak estuary must be questioned confronted to this greening evidence.