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Ensuring a Long-Term Future for Mangroves: A Role for Remote Sensing

A special issue of Remote Sensing (ISSN 2072-4292). This special issue belongs to the section "Remote Sensing in Agriculture and Vegetation".

Deadline for manuscript submissions: closed (31 March 2021) | Viewed by 20334

Special Issue Editors


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Guest Editor
Department of Geography and Earth Sciences, Aberystwyth University, Ceredigion, Aberystwyth SY23 2EJ, UK
Interests: remote sensing; biogeography; ecology; land cover dynamics; forests and coastal ecosystems (including mangroves)
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
French Institute of Pondicherry (IFP) - French National Research Institute for Development (IRD),11 Saint-Louis Street, Pondicherry 605001, India
Interests: remote sensing of mangrove forests for monitoring and modelling their dynamics

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Guest Editor
1. School of Earth and Environmental Science, Faculty of Science, Medicine and Health University of Wollongong, NSW 2522, Australia
2. Department of Primary Industries Fisheries, DPI Fisheries, 12 Shirley Rd, Wollstonecraft, NSW 2065, Australia
Interests: remote-sensing; mangroves; sea-level rise and climate change

Special Issue Information

Dear Colleagues,

Across their range and particularly in recent decades, mangroves have experienced significant loss and degradation through human activities (e.g., clearance or degradation), and have induced coastal and climate change. These changes and the impacts on the coastal environment are particularly noticeable in time-series of remote sensing data. The remote sensing community has reported on such changes at varying (local to global) scales and temporal frequencies and using a diverse range of sensors (primarily optical, radar, and lidar). However, despite alerting communities at all levels to such changes, mangroves continue to be lost or degraded to the point that there are now large sections of coastline with very little of this ecosystem remaining. Such losses are devastating to both floral and faunal diversity, and significantly compromise the integrity and functioning of coastal environments. Moreover, there are significant impacts on societies living close to or relying on mangroves, and also on local to national economies.

Without multi-scale Earth observations, there is no doubt that the community would be far less aware of the changes in mangroves that have occurred, and of the extent of the damage inflicted. However, we can do more, but this requires the whole community to engage and collaborate in a way that ensures that local to international policymakers, land managers, and communities are provided with robust datasets that routinely capture and can be used to report—on a timely and regularly basis—the states and dynamics of mangroves at local to global scales.

The Special Issue "Ensuring a Long-Term Future for Mangroves: A Role for Remote Sensing" in Remote Sensing aims at highlighting research that explores the following:

  1. How the characterizing, mapping, and monitoring of mangroves can be consistently coordinated, from local to global scales, such that the various datasets generated build on and align with each other, particularly in terms of mapped extents, class taxonomies, and biophysical attributes (e.g., height, cover, and biomass).
  2. How in situ (field) data coupled with very high spatial resolution airborne (including drone) and spaceborne images can support the development products and build sound baselines dedicated to emblematic topics such as, "mangroves for sustainable aquaculture" or "mangroves for early warning on coastal erosion", which can be addressed and managed at national and international levels.
  3. How the development of algorithms and models for explaining changes along coastlines supporting mangroves as a function of forcing variables (climate, ocean, and human activities) can prefigure the dynamic and reliable classifications of coastal land cover change and evolution.
  4. How the transboundary issue of mangrove preservation can benefit from centralized repositories with freely available data at a global level.
  5. How local communities can be made increasingly aware of and become involved in the sustainable and equitable management of “their” mangrove region through new technologies including mobile phone applications, web-portals alimented by image data and dynamic land cover maps.
Prof. Richard Lucas
Dr. Christophe Proisy
Dr. Emma Asbridge
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Remote Sensing is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (4 papers)

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Research

20 pages, 32515 KiB  
Article
A Validated and Accurate Method for Quantifying and Extrapolating Mangrove Above-Ground Biomass Using LiDAR Data
by Rafaela B. Salum, Sharon A. Robinson and Kerrylee Rogers
Remote Sens. 2021, 13(14), 2763; https://0-doi-org.brum.beds.ac.uk/10.3390/rs13142763 - 14 Jul 2021
Cited by 5 | Viewed by 3309
Abstract
LiDAR data and derived canopy height models can provide useful information about mangrove tree heights that assist with quantifying mangrove above-ground biomass. This study presents a validated method for quantifying mangrove heights using LiDAR data and calibrating this against plot-based estimates of above-ground [...] Read more.
LiDAR data and derived canopy height models can provide useful information about mangrove tree heights that assist with quantifying mangrove above-ground biomass. This study presents a validated method for quantifying mangrove heights using LiDAR data and calibrating this against plot-based estimates of above-ground biomass. This approach was initially validated for the mangroves of Darwin Harbour, in Northern Australia, which are structurally complex and have high species diversity. Established relationships were then extrapolated to the nearby West Alligator River, which provided the opportunity to quantify biomass at a remote location where intensive fieldwork was limited. Relationships between LiDAR-derived mangrove heights and mean tree height per plot were highly robust for Ceriops tagal, Rhizophora stylosa and Sonneratia alba (r2 = 0.84–0.94, RMSE = 0.03–0.91 m; RMSE% = 0.07%–11.27%), and validated well against an independent dataset. Additionally, relationships between the derived canopy height model and field-based estimates of above-ground biomass were also robust and validated (r2 = 0.73–0.90, RMSE = 141.4 kg–1098.58 kg, RMSE% of 22.94–39.31%). Species-specific estimates of tree density per plot were applied in order to align biomass of individual trees with the resolution of the canopy height model. The total above-ground biomass at Darwin Harbour was estimated at 120 t ha−1 and comparisons with prior estimates of mangrove above-ground biomass confirmed the accuracy of this assessment. To establish whether accurate and validated relationships could be extrapolated elsewhere, the established relationships were applied to a LiDAR-derived canopy height model at nearby West Alligator River. Above-ground biomass derived from extrapolated relationships was estimated at 206 t ha−1, which compared well with prior biomass estimates, confirming that this approach can be extrapolated to remote locations, providing the mangrove forests are biogeographically similar. The validated method presented in this study can be used for reporting mangrove carbon storage under national obligations, and is useful for quantifying carbon within various markets. Full article
(This article belongs to the Special Issue Ensuring a Long-Term Future for Mangroves: A Role for Remote Sensing)
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19 pages, 4478 KiB  
Article
Mapping the Extent of Mangrove Ecosystem Degradation by Integrating an Ecological Conceptual Model with Satellite Data
by Calvin K. F. Lee, Clare Duncan, Emily Nicholson, Temilola E. Fatoyinbo, David Lagomasino, Nathan Thomas, Thomas A. Worthington and Nicholas J. Murray
Remote Sens. 2021, 13(11), 2047; https://0-doi-org.brum.beds.ac.uk/10.3390/rs13112047 - 22 May 2021
Cited by 19 | Viewed by 5021
Abstract
Anthropogenic and natural disturbances can cause degradation of ecosystems, reducing their capacity to sustain biodiversity and provide ecosystem services. Understanding the extent of ecosystem degradation is critical for estimating risks to ecosystems, yet there are few existing methods to map degradation at the [...] Read more.
Anthropogenic and natural disturbances can cause degradation of ecosystems, reducing their capacity to sustain biodiversity and provide ecosystem services. Understanding the extent of ecosystem degradation is critical for estimating risks to ecosystems, yet there are few existing methods to map degradation at the ecosystem scale and none using freely available satellite data for mangrove ecosystems. In this study, we developed a quantitative classification model of mangrove ecosystem degradation using freely available earth observation data. Crucially, a conceptual model of mangrove ecosystem degradation was established to identify suitable remote sensing variables that support the quantitative classification model, bridging the gap between satellite-derived variables and ecosystem degradation with explicit ecological links. We applied our degradation model to two case-studies, the mangroves of Rakhine State, Myanmar, which are severely threatened by anthropogenic disturbances, and Shark River within the Everglades National Park, USA, which is periodically disturbed by severe tropical storms. Our model suggested that 40% (597 km2) of the extent of mangroves in Rakhine showed evidence of degradation. In the Everglades, the model suggested that the extent of degraded mangrove forest increased from 5.1% to 97.4% following the Category 4 Hurricane Irma in 2017. Quantitative accuracy assessments indicated the model achieved overall accuracies of 77.6% and 79.1% for the Rakhine and the Everglades, respectively. We highlight that using an ecological conceptual model as the basis for building quantitative classification models to estimate the extent of ecosystem degradation ensures the ecological relevance of the classification models. Our developed method enables researchers to move beyond only mapping ecosystem distribution to condition and degradation as well. These results can help support ecosystem risk assessments, natural capital accounting, and restoration planning and provide quantitative estimates of ecosystem degradation for new global biodiversity targets. Full article
(This article belongs to the Special Issue Ensuring a Long-Term Future for Mangroves: A Role for Remote Sensing)
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23 pages, 5078 KiB  
Article
Remote Sensing Based Spatial-Temporal Monitoring of the Changes in Coastline Mangrove Forests in China over the Last 40 Years
by Junyao Zhang, Xiaomei Yang, Zhihua Wang, Tao Zhang and Xiaoliang Liu
Remote Sens. 2021, 13(10), 1986; https://0-doi-org.brum.beds.ac.uk/10.3390/rs13101986 - 19 May 2021
Cited by 21 | Viewed by 3226
Abstract
As a developing country, China’s mangrove landscape pattern has undergone significant temporal and spatial changes over the last four decades. However, we know little about the changes in the mangrove landscape pattern characteristics other than the area at the national scale. The analysis [...] Read more.
As a developing country, China’s mangrove landscape pattern has undergone significant temporal and spatial changes over the last four decades. However, we know little about the changes in the mangrove landscape pattern characteristics other than the area at the national scale. The analysis of mangrove landscape pattern changes from different perspectives on a national scale can provide scientific support for mangrove protection and restoration. In this study, the temporal and spatial changes in the pattern of the mangrove landscape over the last 40 years in China were analyzed based on remote sensing data with high classification accuracy (99.3% of 2018). First, according to the natural geographical conditions of the coastal zone and the distribution of the mangroves, the distribution area of the mangroves in China was divided into 31 natural shores. Then, by selecting representative landscape indexes and constructing an integrated landscape index, the spatial-temporal changes in the landscape pattern of China’s mangroves over the last 40 years were analyzed based on five perspectives: Total area change, shape complexity, connectivity, fragmentation, and the integrated state of the landscape. From a temporal viewpoint, before 2000, the total area of each shore exhibited a downward trend, and the degree of connectivity deteriorated continuously, but the degree of fragmentation was stable at a low level. After 2000, although the total area improved, the degree of fragmentation gradually increased. The spatial changes are mainly reflected by the fact that the shores in Guangdong and Hainan exhibited significant differences within the same province. Based on the above analysis, corresponding scientific suggestions are proposed from temporal and spatial viewpoints to provide guidance for mangrove management and protection in China and to provide a reference for mangrove research in other regions of the world. Full article
(This article belongs to the Special Issue Ensuring a Long-Term Future for Mangroves: A Role for Remote Sensing)
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45 pages, 13597 KiB  
Article
Rapid Mangrove Forest Loss and Nipa Palm (Nypa fruticans) Expansion in the Niger Delta, 2007–2017
by Chukwuebuka Nwobi, Mathew Williams and Edward T. A. Mitchard
Remote Sens. 2020, 12(14), 2344; https://0-doi-org.brum.beds.ac.uk/10.3390/rs12142344 - 21 Jul 2020
Cited by 18 | Viewed by 7696
Abstract
Mangrove forests in the Niger Delta are very valuable, providing ecosystem services, such as carbon storage, fish nurseries, coastal protection, and aesthetic values. However, they are under threat from urbanization, logging, oil pollution, and the proliferation of the invasive Nipa Palm (Nypa [...] Read more.
Mangrove forests in the Niger Delta are very valuable, providing ecosystem services, such as carbon storage, fish nurseries, coastal protection, and aesthetic values. However, they are under threat from urbanization, logging, oil pollution, and the proliferation of the invasive Nipa Palm (Nypa fruticans). However, there are no reliable data on the current extent of mangrove forest in the Niger Delta, its rate of loss, or the rate of colonization by the invasive Nipa Palm. Here, we estimate the area of Nipa Palm and mangrove forests in the Niger Delta in 2007 and 2017, using 567 ground control points, Advanced Land Observatory Satellite Phased Array L-band SAR (ALOS PALSAR), Landsat and the Shuttle Radar Topography Mission Digital Elevation Model 2000 (SRTM DEM). We performed the classification using Maximum Likelihood (ML) and Support Vector Machine (SVM) methods. The classification results showed SVM (overall accuracy 93%) performed better than ML (77%). Producers (PA) and User’s accuracy (UA) for the best SVM classification were above 80% for most classes; however, these were considerably lower for Nipa Palm (PA—32%, UA—30%). We estimated a 2017 mangrove area of 801,774 ± 34,787 ha (±95% Confidence Interval) ha and Nipa Palm extent of 11,447 ± 7343 ha. Our maps show a greater landward extent than other reported products. The results indicate a 12% (7–17%) decrease in mangrove area and 694 (0–1304)% increase in Nipa Palm. Mapping efforts should continue for policy targeting and monitoring. The mangroves of the Niger Delta are clearly in grave danger from both rapid clearance and encroachment by the invasive Nipa Palm. This is of great concern given the dense carbon stocks and the value of these mangroves to local communities for generating fish stocks and protection from extreme events. Full article
(This article belongs to the Special Issue Ensuring a Long-Term Future for Mangroves: A Role for Remote Sensing)
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