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The AOI extent is shown using a masked false color composite of Landsat 5 Thematic Mapper (TM) bands 3, 5, and 4, wherein mangrove vegetation appears primarily in vibrant shades of red and orange. The background image is Landsat 5 TM band 4. The location within Madagascar and the national distribution of mangroves (bright green) are shown in the country-wide inset (bottom right: data obtained from Giri [58]).
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Mangroves are found throughout the tropics, providing critical ecosystem goods and services to coastal communities and supporting rich biodiversity. Globally, mangroves are being rapidly degraded and deforested at rates exceeding loss in many tropical inland forests. Madagascar contains around 2% of the global distribution, >20% of which has been d...
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... Known thresholds to determine degradation have been applied, such as canopy density and proportion of coverage (Nayak and Bahuguna 2001). Moreover, indices such as NDVI are commonly used to assess mangrove health, with specific NDVI thresholds indicating the transition from healthy to degraded states (Jones et al. 2015;Valderrama-Landeros et al. 2018). ...
Mangrove ecosystems are essential coastal environments that provide extensive ecological and socioeconomic benefits to both human societies and the natural environment. However, mangrove degradation can lead to significant declines in biodiversity, ecosystem processes, and ecosystem services. Compared to the extensive research focused on documenting mangrove areal changes and deforestation, there is a lack of review on the current status of mangrove degradation identification with the assistance of remote sensing data. This review analyzed 104 papers focusing on remote sensing-based mangrove degradation assessments across tropical and subtropical regions from Web of Science and Google Scholar databases. We summarized the remote sensing approaches employed, the specific proxies or indicators derived from remote sensing data to characterize mangrove degradation, the primary remote sensing datasets utilized and remote sensing image classification methods. We also identified the key challenges (e.g. lack of optimal proxies, confusions between true degradation and natural variability) and emerging opportunities for future research in the remote sensing-based assessment of mangrove degradation. Based on publications, one of the primary challenges lies in the inconsistency of definitions and proxies used to characterize mangrove degradation. Scale effects and the inherent complexity of remote sensing data further compound these challenges. Nonetheless, the increasing availability of advanced multi-source remote sensing data holds promise for more accurate and comprehensive measurement of mangrove degradation, which could ultimately inform and guide sustainable coastal management and restoration efforts.
... Kata kunci : citra satelit, model regresi, kawasan konservasi, stok karbon PENDAHULUAN Ekosistem mangrove merupakan salah satu jenis ekosistem yang menyusun kawasan pesisir. Ekosistem mangrove disusun oleh jenis tumbuhan yang memiliki kemampuan adaptasi terhadap salinitas dan pasang surut air laut, umumnya membentuk zonasi berupa penyebaran jenis yang mengelompok ke arah darat (Yuvaraj et al., 2017;Jones et al., 2015). Ekosistem mangrove berperan penting memberikan jasa lingkungan bagi Kawasan pesisir, keberadaan mangrove berperan sebagai habitat ikan (Vincentius et al., 2019), perlindungan dari badai tropis (Zhang et al., 2022), dan memiliki produktivitas tinggi (Alongi, 2020). ...
Distribution and extent of existing mangroves, conditions, and potential for blue carbon are needed to encourage the economy of coastal communities as coastal ecosystem services. Kayong Utara Regency as one of the regencies in the coastal area of West Kalimantan has the potential for mangroves to be utilized by coastal communities but there has been no ecological study of the potential for blue carbon contained therein. This study aims to map the distribution of mangroves and their conditions and to map the spatial distribution of mangrove carbon stocks in the Kayong Utara Regency. The mapping method for the distribution of existing mangroves is carried out using the visual interpretation method by making a certain false-color RGB composite, the distribution of mangroves is identified using nine key elements of image interpretation. Mangrove conditions were analyzed through mangrove cover using the hemispherical photography method. Mapping of carbon stocks was carried out using a linear regression model formulation of several vegetation index variables and carbon stock values from making observation plots, then analyzed spatially. The research results show that the mangrove area in North Kayong Regency is 20,543.40 ha, spread throughout the district. Mangrove conditions consist of the categories rare 3.92%, moderate 53.07%, and dense 43.01%. Tree density (DBH ≥ 10 cm) from 56 survey points ranged from 100 – 2800 individual ha-1 with AGC values ranging from 4.21 – 1375.74 Mg ha-1. The dominant mangrove species found included Avicennia alba, A. lanata, A. marina, Bruguiera parviflora, Excoecaria agallocha, Rhizophora apiculata, R. mucronata, R. stylosa, Xylocarpus granatum. The best linear regression model in this study uses the MDI2 variable with the formulation y = 225.08x – 114.55 and the Pearson correlation value (r) = 0.377. The AGC potential value of the selected model ranges from 0 – 631.92 Mg ha-1 spread with the largest potential value found in Pulau Maya District. Data sebaran dan luasan mangrove eksisting, kondisi dan potensi karbon biru diperlukan untuk mendorong peningkatan ekonomi masyarakat pesisir sebagai jasa ekosistem pesisir yang masih terbatas saat ini. Kabupaten Kayong Utara sebagai salah satu Kabupaten di wilayah pesisir Kalimantan Barat memiliki potensi mangrove yang dimanfaatkan oleh masyarakat pesisir namun belum ada kajian ekologis tentang potensi karbon biru yang terdapat didalamnya. Penelitian ini bertujuan untuk memetakan sebaran mangrove dan kondisjnya serta memetakan distribusi spasial stok karbon mangrove di Kabupaten Kayong Utara. Metode pemetaan sebaran mangrove eksisting dilakukan dengan menggunakan metode interpetasi visual dengan membuat komposit false-color RGB tertentu, sebaran mangrove diidentifikasi dengan menggunakan sembilan unsur kunci interpetasi citra. Kondisi mangrove dianalisis melalui tutupan mangrove dengan metode hemispherical photography. Pemetaan stok karbon dilakukan dengan formulasi model regresi linear beberapa variabel indeks vegetasi dan nilai stok karbon dari pembuatan plot pengamatan, kemudian dianalisis secara spasial. Hasil penelitian menunjukkan luasan mangrove di Kabupaten Kayong Utara sebesar 20.543,40 ha, tersebar di seluruh Kecamatan. Kondisi mangrove terdiri atas kategori jarang 3,92%, sedang 53,07% dan rapat 43,01%. Kerapatan pohon (DBH ≥ 10 cm) dari 56 titik survey berkisar antara 100 – 2800 ind ha-1 dengan nilai AGC berkisar 4,21 – 1375,74 Mg ha-1. Spesies mangrove dominan yang ditemukan antara lain Avicennia alba, A. lanata, A. marina, Bruguiera parviflora, Excoecaria agallocha, Rhizophora apiculata, R. mucronata, R. stylosa, Xylocarpus granatum. Model regresi linear yang terbaik pada penelitian ini menggunakan variabel MDI2 dengan formulasi y = 225,08x – 114,55 dan nilai korelasi pearson (r) = 0,377. Nilai potensi AGC dari model yang dipilih berkisar antara 0 – 631,92 Mg ha-1 tersebar dengan nilai potensi terbesar terdapat di Kecamatan Pulau Maya.
... UNIMA is the biggest Malagasy shrimp exporter and is praised for its social and environmental commitments (Red and CSA labels) (Monfort & Rajaosafara, 2017;Slobodian & Badoz, 2019). In partnership with the nongovernmental organization WWF, 9 it committed to implement BOs through reforestation as a compensation for the development of a surface area of D = 800 ha to be used as a shrimp farm in Mahajamba bay (45,107 ha) (Darbi, 2020;Jones et al., 2015). The farm has an average productivity of 4.5 tons per year per hectare (Rajaosafara & du Payrat, 2009) and its marginal return rate without offset is here estimated 10 to g = 70, 000 US$ ha −1 . ...
Biodiversity offsets (BOs) are increasingly used as economic instruments to manage biodiversity and ecosystem services in the context of economic development. This study investigates the sustainability conditions of BOs. It focuses especially on both the timing and pricing of BOs in development‐offset projects. To address this issue, a minimal time control model is proposed, allowing a dynamic and multicriteria approach to be combined through both ecological and economic targets. We rely here on no net loss (NNL) and positive net present value (NPV) goals. In particular, we focus on an offset marginal price, called offset sustainability price (OSP), which equalizes the NNL and payback times. We prove analytically how this OSP pricing corresponds to a win–win solution in terms of ecological‐economic synergy. We also show that this OSP pricing can be very high compared to the project rate of return, particularly when the biodiversity loss is high. More globally, a static comparative analysis shows the extent to which the economic and biodiversity parameters impact the OSP. Finally, a numerical application related to mangroves and aquaculture in Madagascar illustrates the analytical findings. For this case study, we argue that the current BO price is underestimated.
Recommendations for Resource Managers:
The biodiversity recovery time to reach the no net loss (NNL) is not sufficiently taken into account in biodiversity offsets (BOs).
An offset sustainability price (OSP), reconciling the profitability and NNL times, is calculated, thus strengthening the developer‐pays principle of BOs.
The OSP is the minimal offset price such that the developer is financially beneficial only after the biodiversity recovery.
The OSP depends nonlinearly on both the developed surface area, the biodiversity initial states and dynamics as well as the economic parameters.
With low discount rates, a multiplier effect simplifies the calculation of the OSP.
... Although historic forest cover change in Madagascar was most likely triggered by climatic changes (Crowley et al. 2021, Joseph et al. 2020, Solofondranohatra et al. 2018, recent deforestation in the study region is mainly driven by human subsistence and some commercial activities like agricultural expansion, livestock grazing or forest exploitation for charcoal production (Dave et al. 2016, Gaydes-Combes et al. 2017, Jones et al. 2015, Steffens et al. 2020. As in other regions of sub-Saharan Africa ...
Forest loss is a main driver of biodiversity decline, particularly in tropical regions. In this study, we investigate the degree of deforestation in the entire ranges of nine highly threatened lemur species in northwestern Madagascar. Landsat satellite images were acquired from four different years (1990, 2000, 2011, 2020), classified into forest/non-forest, and changes quantified. Forest cover has declined from 17.5% to 9.3% within the last 30 years. This decline varied across four protected areas (PAs) investigated: the forest cover of Ankarafantsika National Park (ANP) declined only moderately over time (from 76.3% to 67.4%), while it declined drastically in other PAs (e.g., from 54.9% to 18.9%, Bongolava Forest Corridor). Two lemur taxa are most affected (Lepilemur otto, Mi-crocebus bongolavensis) by this development. For two other species (L. ahmansoni, L. aeeclis), most of the remaining forest is concen-trated in two coastal PAs (in total 627.2 and 477.9 km², respectively), while those species occurring inside ANP (5 taxa) experienced rather stable forest coverage until 2020. A reversal of these deforestation trends and active reforestation measures are desperately needed and can be initiated following an outlined workflow of site selection, tree species selection, nursing of saplings, preparation of sites and follow-up care.
... The overall density of the plantation in BdA, 4628 ± 317 propagules per hectare, surpassed the highest density recorded within the undisturbed tall, mature stands and canopy > 80% closed, Ceriops tagal dominated mangrove in the bay, 3927 ± 244 stem per hectare [39]. Similarly, this density was higher compared with the density of the mixed species stands in both Ambaro-Ambaja and Mahajamba' bays, 1108 ± 208 and 1825 ± 248 trees/ha −1 respectively [38,48]. Also higher compared with the stand density of mangroves in Ngomeni, Kenya, with 1688 stems per hectare for Rhizophora mucronata dominated and 2367 stems per hectare for Ceriops tagal dominated [49]. ...
... Also higher compared with the stand density of mangroves in Ngomeni, Kenya, with 1688 stems per hectare for Rhizophora mucronata dominated and 2367 stems per hectare for Ceriops tagal dominated [49]. However, the density of the plantation in the BdA was lower compared with the highest number of trees per hectare recorded within the tall, mature stands of trees Rhizophora mucronata dominated, recorded in Mahajamba, 4900 ± 1500 trees/ha −1 [48], and within the highest density recorded within intact, tall and mature stands dominated by Rhizophora mucronata recorded in Ambaro-Ambanja bays, 4719 ± 1133 trees/ha −1 [38]. Additionally, this is lower compared with the highest density of mature trees recorded on the eastern coast of Madagascar, 7960 tree/ha −1 [50]. ...
Local communities play a key role in ecosystem restoration due to their invaluable traditional ecological knowledge. While community-led mangrove restoration has been practiced in Madagascar for decades, the factors influencing the success of the restoration remains understudied. Despite the extensive local knowledge, the complexity of factors influencing restoration success requires outside technical expertise. This study aimed to investigate the drivers of mangrove restoration success in southwest Madagascar. The survival rate of mangroves planted from 2015 to 2022, including Rhizophora mucronata, Bruguiera gymnorrhiza, and Ceriops tagal was assessed using the sampling methods for tree planting inventory with circular plots. R version 4.2.2 was used for descriptive statistics analysis. The correlation between the survival rate and plantation density, species composition, and number of participants was assessed using a Principal Component Analysis. As a result, the mean survival rate of the 440,990 planted mangroves, with a density of 4628 ± 317 trees/ha⁻¹ was 82.5 ± 1.8%. Our study showed that plantation density and species composition are not correlated with survival rate. However, the survival rate is inversely correlated with the number of participants. The findings of this paper showed that both traditional ecological knowledge and scientific observations are vital to informing mangrove reforestation.
... Landsat data series are the most broadly used among the existing optical datasets, because they are freely available for mapping long-term observations at different spatial scales (Jones et al., 2014(Jones et al., , 2015(Jones et al., , 2016Goïta et al., 2017). Optical remote sensing data can be used to map carbon stocks in mangroves with different parametric approaches, including multiple regression models, vegetation indices, non-parametric machine learning approaches (Jachowski et al., 2013), and can also be estimated from canopy parameters and mangrove species Candra et al., 2016;Tang et al., 2018). ...
... Their analysis demonstrated a net loss of 3.18% between 2002 and 2014 with total estimated carbon stock of the 1507 ha of mangroves as 5.84 ± 0.35 (Mg × 10 5 ), with the 95% confidence interval equivalent to ±0.70 × 10 5 of the overall mean. Using similar methodologies, Jones et al. (2014Jones et al. ( , 2015Jones et al. ( , 2016 Jachowski et al. (2013) used GeoEye-1 and a machine learning algorithm in combination with ASTER GDEM elevation data to estimate and map AGB and BGB in Southwest Thailand with a statistically significant result (p < 0.0001 and R 2 = 0.66). ...
... In areas of active sediment deposition and coastal extension, such as river deltas, such changes can be quite rapid (Lebigre 1988), but elsewhere mangroves in Malagasy waters can be relatively stable with little discernible change over decades (e.g., Be Totozafy 1994;Frontier-Madagascar 2003). T. Jones et al. 2015, Benson et al. 2017, Rakotomavo 2018 Anthropogenic activities are causing increased mangrove degradation and deforestation in many areas (T. Jones et al. 2016a). ...
... More than 20% of Madagascar's mangrove ecosystems have been heavily degraded or deforested since 1990, owing primarily to increased harvest for charcoal and timber and the expansion of agriculture and aquaculture (T. Jones et al. 2015Jones et al. , 2016a. This has been documented in several known historical habitats for sawfishes (e.g., T. Jones et al. 2016a). ...
This chapter in the New Natural History of Madagascar (Goodman ed. 2022, Princeton University Press) provides the most comprehensive account to date of scientific knowledge of the natural history of Madagascar's marine and coastal ecosystems and their biodiversity, including marine megafauna (including cetaceans, dugong, sea turtles, sharks, rays, sawfishes and coelacanth (Latimeria chalumnae).
... The maximum likelihood algorithm was used for the classification of these images and to produce maps of class distributions. The maximum likelihood method is widely used [26,41,[47][48][49] because of its ability to classify pixels on a probabilistic basis by highlighting the standard margin of error between pixel values and those of different areas of interest [50]. Preclassification operations making radiometric and geometric corrections using ENVI software served to improve the quality of the images before processing. ...
... The maximum likelihood algorithm was used for the classification of these images and to produce maps of class distributions. The maximum likelihood method is widely used [26,41,[47][48][49] because of its ability to classify pixels on a probabilistic basis by highlighting the standard margin of error between pixel values and those of different areas of interest [50]. ...
Land and resource use patterns in coastal areas play a key role in the resilience of ecosystems and populations to climate change. Knowing their spatiotemporal dynamics therefore constitutes a strategic tool to help decision-makers. Based on documentary research, geographic information system (GIS), image processing, and field work, this article maps land use on Manoka Island between 1986 and 2018 and identifies the drivers of change and avenues for intervention with a view to strengthening climate change mitigation. The results show a decrease of 4% in forest area on Manoka Island, representing an average of 112 ha of inland forest and 267 ha of mangrove converted between 1986 and 2018. This increases the degraded forest area by 268% (degraded mangrove and degraded inland forest) and exposes some camps to erosion and flooding. Reduction in forest area is mainly linked to the harvesting of fuelwood and the conversion of forests into farmland and residential areas. Settlements have increased in area from 15 ha in 1986 to 90.4 ha in 2018 to the detriment of natural spaces.
... Fire frequency was surprisingly high in coastal mangroves, with the highest average singlemonth (November) fire frequency of any ecoregion. Mangrove forests mitigate erosion [52] and provide resources and aquaculture opportunities to local people [53], but in Madagascar they are being harvested at unsustainable rates [54][55][56]. The noteworthy fire use in this semiaquatic ecosystem reflects the high anthropogenic pressures that Madagascar's mangroves face. ...
Anthropogenic fire use is widespread across Madagascar and threatens the island’s unprecedented endemic biodiversity. The vast majority (96%) of lemur species are already threatened with extinction, and Madagascar has already lost more than 44% of its forests. Previous conservation assessments have noted the role of fire in the rampant deforestation and habitat degradation across Madagascar, but published, quantified data on fire use across the island are incredibly limited. Here, we present the first quantification of spatiotemporal patterns in fire occurrence across Madagascar using VIIRS satellite fire detection data. We assess which regions of Madagascar have the most prevalent fire use, how fire use is changing over time, and what this means for Madagascar’s remaining forest ecosystems. An average of 356,189 fires were detected every year in Madagascar from 2012–2019, averaging 0.604 fires/km². Fire use was near-ubiquitous across the island, but was most prevalent in the western dry deciduous forests and succulent woodlands ecoregions. Fire frequency in the eastern lowlands was highest around the remaining humid rainforest, and fire frequency was increasing over time around much of the remaining humid and dry forest. We found that 18.6% of all remaining forest was within 500 m of a fire within a single year, and 39.3% was within 1 km. More than half of remaining forest was within 1 km of a fire in a single year in the dry deciduous forests, succulent woodlands, and mangroves ecoregions. However, fire frequency within national park protected areas was, on average, 65% lower than their surroundings. Only 7.1% of national park forest was within 500 m of a fire within one year, and 17.1% was within 1 km, suggesting that national parks are effective at reducing fire frequency in Madagascar’s tropical forests.
... The potential for biophysical dispersal models using simulated dispersal patterns to incorporate demographic connectivity are insightful. However, more empirical studies on individual species and their dispersal kernels (the probability distribution of larvae as a function of their starting location) is required to fine-tune the input of biological data for ground truthing these models (Moilanen 2011;Jones 2015;Manel et al. 2019). We found strong evidence for a linkage of method choice with study scope, suggesting that planners varied in the value they placed on ecological processes in planning assessments. ...
Marine-protected areas are designated to reduce anthropogenic impacts on biodiversity and enhance fish production, but other ecological processes are inadequately accommodated in plans for coastal and marine ecosystems. We conducted a quantitative systematic literature review and meta-analysis on how researchers and decision-makers include ecological processes in coastal and marine conservation planning. Marine spatial planning ideally delivers representative protected areas systems that deliver persistence for ecosystems and species. Although several reviews have reported on incorporating connectivity as a process in marine spatial planning, to our knowledge, no one has yet published an inclusive review on how ecological processes are incorporated to help ensure persistence in coastal and marine planning. A total of 162 peer-reviewed journal research papers and 27 non-peer-reviewed papers (n = 189) were identified that included ecological processes in coastal and marine conservation planning between 2000 and 2019, the number of papers integrating ecological processes peaked in 2013 followed by a declining trend to 2019. We attribute the trend to the complexity of the problem of integrating dispersal and demographic objectives alongside other management goals. The results of our statistical analysis uncovered that incorporating ecological processes in conservation planning is important for coastal and marine ecosystems across the literature (p-value < 0.001). However, there was significant variation in scope and choice of method in planning assessments. Dispersal was the process most frequently incorporated in spatial plans, followed by demography and flows of nonliving materials. Identifying appropriate ecosystem objectives and incorporating multiple sources of uncertainty into conservation planning for coastal and marine ecosystems remain important areas for future research. This review highlights the need for greater awareness among planners of the relevance of ecological processes in conservation planning for coastal and marine ecosystems.
