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Wetlands’ Inventory, Mapping and Land Cover Index Assessment on Mauritius
Abstract and Figures
Past studies conducted on wetlands of Mauritius lead to the conclusion that half of the wetlands have been backfilled for touristic and housing development and that the ecological condition of the remaining wetlands is being seriously challenged by numerous threats, natural and anthropogenic. This research aimed to fill the information gap concerning wetland type and distribution. For this, using published maps and satellite imagery, wetlands were digitised resulting in 144 wetlands and categorised into 8 ecological units. Afterwards, a number of wetlands were ranked according to their environmental condition based on a series of Land Cover Indices (LCIs). These indices were derived by analysis of land cover types and slope gradient within a 50 m and a 950 m watershed-bounded buffer zone. Wetlands in forested areas were the least disturbed, with LCI of typically 0.30, but potentially threatened by sediment accumulation due to a high slope gradient (>20 %). Three wetlands in Mauritius are classified as Ramsar wetland. One of them, the Blue Bay Marine Park (BBMP) has moderately good condition (LCI = 0.55). The other one, the Rivulet Terre Rouge Estuary Bird Sanctuary (RTREBS) was among the most heavily impacted (LCI = 0.87) due to intensive urbanization.
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... The exploitation of wetlands for infrastructure development has reduced the Fthe natural hydrological buffering capacity, increasing flood incidences and intensity. Approximately 70% of wetland extent in the northern coastal region has been lost, exacerbating flooding in the region (Mamoun et al., 2013). ...
... The challenges of climate change on infrastructure in Mauritius are further compounded by inadequate maintenance of drainage facilities. Surveys indicate that poorly maintained drainage systems, clogged culverts, and blocked waterways by debris and garbage are primary reasons for increased flooding events (Mamoun et al., 2013). The 2013 flash floods, which resulted in 11 fatalities, underscore the need for robust institutional and policy mechanisms to mitigate disaster risks (Government of Mauritius, 2021b). ...
This technical report provides an overview on Mauritius, a Small Island Developing State (SIDS) in the Indian Ocean. The overall purpose is to provide a state-of-the-art review on the climate and resource-use challenges in Mauritius, and ongoing efforts to address some of these. The report begins by providing the big picture, or context of SIDS more generally, and the unique development, economic, and climate challenges they face. After a brief country background on Mauritius, the report details how climate change is impacting Mauritius’ critical resources such as water, energy, food, and infrastructure. The review ends with ongoing adaptation measures adopted by this small island nation.
... The exploitation of wetlands for building and infrastructure construction reduces the natural hydrological buffering capacity to rainwater runoff. About 70% of wetland extent in the northern coastal region of Mauritius has been lost, resulting in increased incidences and intensity of flooding in the region [11]. The construction of drains with inadequate carrying capacities and the allocation of building permits in low-lying, flood-prone areas further exacerbate the flood problem on the island [12]. ...
... The construction of drains with inadequate carrying capacities and the allocation of building permits in low-lying, flood-prone areas further exacerbate the flood problem on the island [12]. Based on the result of a recent survey, victims of flooding events in Mauritius were of the opinion that poorly maintained drainage facilities, as witnessed through clogged culverts and blocked waterways by debris and garbage, was the primary reason for the increase in flooding events recorded in their localities [11]. ...
Economic growth and population expansion in Mauritius have driven unprecedented rates of development. Most notably, increased urbanization of flood-prone regions has exacerbated challenges around resilience and vulnerability to recurrent flooding. We implement a multi-criteria model consisting of a physical-oriented, a social-oriented and an economic-oriented scenario to identify highly vulnerable sites to flooding in the capital city, Port Louis. Social, technical, economic and legal perspectives are incorporated to propose comprehensive flood management strategies. The aim is to minimize the physical impacts of floods while also addressing the broader social and economic risks. Location-based flood management strategies are thereafter proposed to increase the resilience of the city to flooding. Measures include, inter alia, the construction of an underground stormwater storage tank at Champ de Mars, establishment of flood refugee camps at Vallée Pitot and Cité La Cure, reviewing building regulations and urban planning, replacement of the Caudan Underpass by an Overhead Bridge, green renaturing of rivers in downstream areas, construction of a retention pond on the downhill slope of the mountain at Bell Village, and the setting up of a diversion tunnel linking St Louis River to Grand River North West. The approach adopted will allow an understanding of the geography of flooding in Port Louis and support management decisions for limiting its impacts.
... org/ maps/ map/ 3097). The data on coral reef extent and protected marine areas followed UNEP (2021), mangroves patches were situated following Mamoun et al. (2013) and Hammond et al. (2015) Content courtesy of Springer Nature, terms of use apply. Rights reserved. ...
Small island developing states (SIDS) display high biodiversity but are disproportionately vulnerable to climate change and economic and environmental shocks. In Mauritius, located east of Madagascar in the Indian Ocean, mangroves provide essential ecological services and support coastal communities’ livelihoods, but are threatened by continuous degradation. While regulating and provisioning services of mangroves are well documented, our study elucidates some of the lesser-known cultural values attached to mangroves and the ways in which communities depend on them for their well-being. Using a multi-dimensional ecosystem services framework, we conducted an in-person survey between August and October 2021 in coastal villages in east-southeast Mauritius of 281 Mauritian households in middle- to low-income categories with livelihoods associated to fishing and/or tourism. We analysed the data through distribution analysis, multiple correspondence analysis, and logarithmic regression. Our results show that two-thirds of respondents depend on mangroves with low (37.2%) to medium and high (26.3%) dependencies for cultural services and as a support for food security and income generation. Socio-economic drivers and multiple crises play a direct and indirect role in mangrove dependency. Our results suggest that precarious households have higher levels of dependency and are consequently more vulnerable to mangrove degradation and socio-ecological changes. The impact of changes and socio-economic parameters are therefore essential dimensions for coastal management and biodiversity conservation policy design.
... org/ maps/ map/ 3097). The data on coral reef extent and protected marine areas followed UNEP (2021), mangroves patches were situated following Mamoun et al. (2013) and Hammond et al. (2015) Content courtesy of Springer Nature, terms of use apply. Rights reserved. ...
https://charlestelfaircentre.com/mangroves-are-essential-for-coastal-livelihoods-and-local-resilience-insights-from-mauritius/?fbclid=IwAR2t3iAvHcaNOAdeg4Ul65w7GuiFyR0MxHO0UoRne9VIcEVQ3muIV5d3T00
... Being a contracting party of the Ramsar Convention since September 2001 (Mamoun et al., 2013), the island has three Ramsar sites (GoM, 2018a). This intergovernmental treaty restricts contracting parties from the 'unthinking, selfish exploitation of their sovereign natural patrimony' (Matthews, 1993). ...
Flood Management
Policy Research
Disaster Management
... This wetland deterioration has been further accompanied by significant losses of biodiversity and degradation of ecological functions (Kak, 2010;Pandit, 2008). As a result, systematic water quality and LULC monitoring of wetland ecosystems are important for understanding the role of catchment areas (Mamoun et al., 2013;Saah et al., 2019). Therefore, wetland management, urban planning, and development must be well-thought-out in a comprehensive manner, involving all stakeholders like government departments, academia, non-governmental organizations, and civil society. ...
The knowledge on urban ecosystem dynamics is being increasingly felt due to unprecedented symptoms arising out of urbanization. This study is aimed to assess land use-land cover changes (LULCCs) around a wetland ecosystem using high spatial resolution CORONA and Google Basemap satellite imageries. The imageries were processed by digitizing land cover features at 1:3000 scale in ArcGIS 10.1. The imageries were classified into nine classes, and an estimation of accuracy was performed utilizing the Kappa coefficient and error matrices. The overall accuracy obtained was 94% for the 2017 dataset. The key findings indicated a loss of 23% in the wetland area from 1980 to 2017. While in the vicinity, a significant increase in green spaces (706.2%) and roads (89.4%) was observed. Morphometric analysis revealed that the wetland has lost a surface area of 10.2 ha from 1980 to 2017. The maximum length (Lmax) of the wetland was reduced by 722 m while the maximum width (Wmax) decreased by 78 m. Bathymetric analysis revealed that the wetland is shallow with a depth ranging from 10 to 174 cm. The Carlson’s Trophic State Index (TSI) of wetland ranging from 74 to 87 indicates hyper-eutrophic waters. Overall, the loss of wetland area, together with the reduction in morphometric features, low depth, and higher trophic status speak of anthropogenic pressures that are compromising the ecological integrity of this wetland. Therefore, landscape planning and governance are of pivotal importance for the conservation and management of wetland ecosystems in this region.
... The supply of high-quality environmental data expands considerably when using these spatial information technologies (Yang et al., 2016a). Various landscape-level indicators, such as land-cover type, landscape fragmentation, slope gradient, wetland area, and aquatic connectivity, have been adopted to represent wetland conditions (Brooks et al., 2004;Mamoun et al., 2013;Weller et al., 2007). Based on these indicators, a variety of methods have been applied to infer and assess wetland conditions. ...
Wetlands are one of the most valuable natural resources on earth and play an important role in preserving biodiversity. However, due to economic development and human disturbances, many wetlands across the world have deteriorated and disappeared over the past several decades. By using remote sensing images and point of interest (POI) data, we proposed a knowledge-based raster mapping (KBRM)-based framework and implemented it in the assessment of wetland ecological conditions in Suzhou, China. Density maps of waterbodies, vegetation covers, imperviousness, roads, and POI values were derived and used as five ecological indicators that can represent the ecological conditions of wetlands. The KBRM approach was used to integrate these indicators into an overall rating and map wetland ecological conditions efficiently. Thus, spatial variations in wetland ecological conditions can be distinguished and represented in detail. Cross validation was conducted with water quality data at 15 field sampling sites. The validation results demonstrated that the overall wetland condition scores generated by our approach and the water quality index (WQI) values calculated from water quality data were strongly correlated. These findings confirm that our framework could be used to effectively map and evaluate spatial variations in wetland ecological conditions and provide more support for policy-making in wetland protection and management
Small island developing states (SIDS) display high biodiversity due to their insular situation but suffer from a disproportionate vulnerability to climate change, economic and environmental shocks. In Mauritius, a SIDS located the Indian Ocean, mangroves ensure essential ecological functions and support coastal communities’ livelihoods, they are however threatened by continuous degradations. In 2020, communities on the southeast of the island experienced compounded overlapping effects of a global pandemic and an ecological crisis, with impacts on livelihoods and well-being. This same area is known for its extent of mangroves. While regulating and provisioning services of mangroves are well documented, this study elucidates some of the lesser-known cultural values attached to mangroves and the ways in which communities depend on them for their well-being. Based on a multi-dimensional ecosystem services framework, an in-person survey was implemented between August and October 2021 in coastal villages on the east-southeast of Mauritius, totalling 281 surveyed households of Mauritians in middle- to low-income categories with livelihoods associated to fishing and/or tourism. The collected data was analysed through distribution analysis, multiple correspondence analysis and logarithmic regression. Our results show that two thirds of respondents depend on mangrove ecosystem services with low (37.2%) to medium and high (26.3%) dependencies. Dependency on mangroves is materialized through cultural services, and as a support for food security and income generation. Socio-economic drivers and multiple crises play a direct and indirect role in mangrove dependency. Study results suggest that precarious households have higher levels of dependency, and are subsequently more vulnerable to mangroves degradation and socio-ecological changes. The impact of changes and socio-economic parameters are therefore essential dimensions to take into account for coastal management and biodiversity conservation policy design in an insular context.
Globally, urban wetlands are facing immense pressure from land use land cover changes (LULCCs) and associated water quality degradation that is severely affecting the trophic status of these ecosystems. This study analyzed water quality degradation resulting from land system changes in the vicinity of Khushalsar, an urban Wetland , in Srinagar City from 1980 to 2017. The analysis of satellite data indicated that this Wetland lost~18.1 ha from 1980 to 2017. During the same period, the urban area within the Wetland increased from 0.2% to 16.5%. The land cover changes assessed in the vicinity of Wetland indicated an increase of 119% and 62.8% in built-up and roads respectively. The analysis of surface water quality of the Wetland showed widespread degradation. The Trophic state index ranged from 73.4 to 84.6 indicating hyper-eutrophic waters. A snapshot of comparative water quality data from 2002 to 2018 revealed that the mean concentration of NO 3 −-N increased from 219 to 433 μg L −1 and that of total phosphorus increased from 135.4 to 1,236 μg L −1 indicative of continuous nutrient enrichment. Hierarchical cluster analysis (HCA) grouped eight sampling sites into four clusters based on likeliness of water quality characteristics. Similarly, discriminant analysis showed the formation of similar patterns of clusters, corroborating the HCA. Principal component analysis suggested three principal components accounting for a cumulative variance of 90.61%. The unplanned land system changes visa -vis human-induced water quality degradation together with the lack of a monitoring mechanism have brought the Khushalsar Wetland to its current hyper-eutrophic state.
Soil erosion by water is one of the most important natural resources management problems in the world. The damages it causes on-site are soil loss, breakdown of soil structure, and decline in organic matter content, nutrient content, fertility, and infiltration rate. Lands with the highest erosion risk on Mauritius Island are crop cultivations (sugarcane, tea, vegetables) on erosion-susceptible terrain (slopes >20% coupled with highly erodible soils). The locations of such lands on Mauritius were mapped during previous, qualitatively based regional-scale erosion studies. In order to propose soil conservation strategies, there is a need to apply a more quantitative approach to supplement the previous, qualitatively based studies. This paper reports an application of the Revised Universal Soil Loss Equation (RUSLE) within a geographical information system in order to estimate soil loss on the island, and particularly for the high-erosion areas. Results show that total soil loss on the island is estimated at 298 259 t year–1, with soil loss from high-erosion areas summing 84 780 t year–1 (28% of total soil loss). If all of the high-erosion areas were afforested, their soil loss would be reduced to 10 264 t year–1, i.e. a reduction of 88% for the high-erosion areas and a reduction of 25% for the island. This study thus calls for soil and water conservation programs directed to these erosion-prone areas before the land degradation and environmental damage they are causing become irreversible. The methodological approach used in this work to quantitatively estimate soil loss from erosion-prone areas can be adopted in other countries as the basis for a nationwide erosion assessment in order to better inform environmental policy needs for soil and water conservation.
Depressional wetlands in agricultural landscapes are easily degraded by sediments and contaminants accumulated from their
watersheds. Several best management practices can reduce transport of sediments into wetlands, including the establishment
of vegetative buffers. We summarize the sources, transport dynamics, and effect of sediments, nutrients, and contaminants
that threaten wetlands and the current knowledge of design and usefulness of grass buffers for protecting isolated wetlands.
Buffer effectiveness is dependent on several factors, including vegetation structure, buffer width, attributes of the surrounding
watershed (i.e., area, vegetative cover, slope and topography, soil type and structure, soil moisture, amount of herbicides
and pesticides applied), and intensity and duration of rain events. To reduce dissolved contaminants from runoff, the water
must infiltrate the soil where microbes or other processes can break down or sequester contaminants. But increasing infiltration
also diminishes total water volume entering a wetland, which presents threats to wetland hydrology in semi-arid regions. Buffer
effectiveness may be enhanced significantly by implementing other best management practices (e.g., conservation tillage, balancing
input with nutrient requirements for livestock and crops, precision application of chemicals) in the surrounding watershed
to diminish soil erosion and associated contaminant runoff. Buffers require regular maintenance to remove sediment build-up
and replace damaged or over-mature vegetation. Further research is needed to establish guidelines for effective buffer width
and structure, and such efforts should entail a coordinated, regional, multi-scale, multidisciplinary approach to evaluate
buffer effectiveness and impacts. Direct measures in “real-world” systems and field validations of buffer-effectiveness models
are crucial next steps in evaluating how grass buffers will impact the abiotic and biotic variables attributes that characterize
small, isolated wetlands.
This paper reports the mapping of monthly soil erosion risk on Mauritius which was carried out using GIS, decision rules and readily available data namely, monthly rainfall depth, soil types, slope and land cover. Slope and soil were first combined to produce soil erosion susceptibility followed by land cover to produce erosion sensitivity, and then rainfall to produce erosion risk. The high erosion areas of the Island have been extracted from the soil erosion risk maps, whereby these areas can face land degradation problems and can be responsible for sediment discharge into wetlands located at the outlet of drainage basins. As such, drainage basins have been delineated using automatic catchment delineation tools and their percentage of high erosion areas computed. Basins with the greatest percentage of high erosion areas and particularly those that directly have a wetland at the outlet can be given priority for soil and water conservation efforts. The mapping reported in this paper can be adapted to other countries which need an erosion assessment for the identification of high erosion areas and priority action areas.
The numerous estuarine, marshy and marine ecosystems along the coastline of Mauritius Island are potential sinks for sediment especially during intense rainfall events when delivery ratios are high at basin outlets. For sustainable environmental management, soil and water conservation measures are needed, as these will better protect the cultivated lands and aquatic ecosystems from the damages associated with excessive soil loss and sediment deposition. Conservation program usually requires focusing available resources on a limited number of priority action areas. Such areas typically have the highest erosion risk and are connected to aquatic ecosystems. An erosion risk mapping model has been applied in this work to find the priority action areas of Mauritius and new datasets representing rainfall erosivity and topographic factors were used compared to a previous application of the same model. Rainfall erosivity was mapped with Fournier Index instead of rainfall depth. The topographic effect was mapped using a function combining slope length and slope gradient (LS) and was based on the unit contributing area algorithm along with land parcels effect. These new datasets improved the erosion risk mapping and the identification and prioritisation of high erosion areas. The prioritisation was done at basin and subbasin scales and considered the location of wetlands. This enabled the identification of basins and subbasins with the greatest erosion risk and towards which conservation measures can be directed for protecting lands on-site and wetlands off-site from environmental damages.
“The Geology and Water Resources of Mauritius” represents the state of knowledge of water resources development in Mauritius at the time it was published. It is an accumulation of some fifteen years experience obtained at the Central Water Authority and other organisations producing an environment conducive to an advance in technical and professional practice.
Wetlands occur in geologic and hydrologic settings that enhance the accumulation or retention of water. Regional slope, local relief, and permeability of the land surface are major controls on the formation of wetlands by surface-water sources. However, these landscape features also have significant control over groundwater flow systems, which commonly play a role in the formation of wetlands. Because the hydrologic system is a continuum, any modification of one component will have an effect on contiguous components. Disturbances commonly affecting the hydrologic system as it relates to wetlands include weather modification, alteration of plant communities, storage of surface water, road construction, drainage of surface water and soil water, alteration of groundwater recharge and discharge areas, and pumping of groundwater. Assessments of the cumulative effects of one or more of these disturbances on the hydrologic system as related to wetlands must take into account uncertainty in the measurements and in the assumptions that are made in hydrologic studies. For example, it may be appropriate to assume that regional groundwater flow systems are recharged in uplands and discharged in lowlands. However, a similar assumption commonly does not apply on a local scale, because of the spatial and temporal dynamics of groundwater recharge. Lack of appreciation of such hydrologic factors can lead to misunderstanding of the hydrologic function of wetlands within various parts of the landscape and mismanagement of wetland ecosystems.