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L-Band Polarimetric Target Decomposition of Mangroves of the Rufiji Delta, Tanzania
Stockholm University, Faculty of Science, Department of Physical Geography.
Stockholm University, Faculty of Science, Department of Physical Geography. University of Dar es Salaam, Tanzania.
Stockholm University, Faculty of Science, Department of Physical Geography.
2016 (English)In: Remote Sensing, ISSN 2072-4292, E-ISSN 2072-4292, Vol. 8, no 2, UNSP 140Article in journal (Refereed) Published
Abstract [en]

The mangroves of the Rufiji Delta are an important habitat and resource. The mangrove forest reserve is home to an indigenous population and has been under pressure from an influx of migrants from the landward side of the delta. Timely and effective forest management is needed to preserve the delta and mangrove forest. Here, we investigate the potential of polarimetric target decomposition for mangrove forest monitoring and analysis. Using three ALOS PALSAR images, we show that L-band polarimetry is capable of mapping mangrove dynamics and is sensitive to stand structure and the hydro-geomorphology of stands. Entropy-alpha-anisotropy and incoherent target decompositions provided valuable measures of scattering behavior related to forest structure. Little difference was found between Yamaguchi and Arii decompositions, despite the conceptual differences between these models. Using these models, we were able to differentiate the scattering behavior of the four main species found in the delta, though classification was impractical due to the lack of pure stands. Scattering differences related to season were attributed primarily to differences in ground moisture or inundation. This is the first time mangrove species have been identified by their scattering behavior in L-band polarimetric data. These results suggest higher resolution L-band quad-polarized imagery, such as from PALSAR-2, may be a powerful tool for mangrove species mapping.

Place, publisher, year, edition, pages
2016. Vol. 8, no 2, UNSP 140
Keyword [en]
mangroves, synthetic aperture radar, polarimetry, ALOS PALSAR, deltas, Rufiji, L-band
National Category
Physical Geography
Research subject
Physical Geography
Identifiers
URN: urn:nbn:se:su:diva-128044DOI: 10.3390/rs8020140ISI: 000371898800035OAI: oai:DiVA.org:su-128044DiVA: diva2:912246
Available from: 2016-03-16 Created: 2016-03-16 Last updated: 2016-04-14Bibliographically approved
In thesis
1. Causes and Perceptions of Environmental Change in the Mangroves of Rufiji Delta, Tanzania: Implications for Sustainable Livelihood and Conservation
Open this publication in new window or tab >>Causes and Perceptions of Environmental Change in the Mangroves of Rufiji Delta, Tanzania: Implications for Sustainable Livelihood and Conservation
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Mangroves are ecosystems with enormous ecological importance, supporting both terrestrial and marine food webs. They provide ecosystem services (e.g. food, medicines, fuel, constructing material) to communities near and far. Despite their importance, mangrove areas are facing numerous threats. Based on neo-Malthusian narratives, population growth is an alleged main cause of mangrove degradation, especially in developing countries. This thesis investigates the Rufiji Delta mangroves, from several perspectives including: recent history, present condition, use of land and other resources, as well as actual and potential impacts of government policies and management on mangrove conservation and for the local communities. Of special interest is the examination of multiple, and often diverging, perceptions concerning these variables and processes. Both qualitative and quantitative methods have been used. Interviews were conducted with relevant stakeholders. Analysis of census data (1957–2012), to ascertain population trends in the Delta, spans the pre- and post-Ujamaa villagization programme. Old maps were scanned and geo-referenced in GIS to compare administrative units between successive censuses. Synthetic Aperture Radar (SAR) imagery, spanning from 1994 to 2010, was explored for analysis of mangrove dynamics and stand structure. The analysis of population trends in the Delta revealed decreasing population in the South Delta and a low population increase in the North Delta, in comparison with neighbouring non-delta areas. This is contrary to the assumption by government authorities that the Ujamaa villagization programme instigated migration to the Delta which caused mangrove degradation. Spatio-temporal changes in mangrove area and land use, observed and confirmed by SAR imagery and field control, is part of the highly dynamic eco-hydrology and geomorphology of the delta ecosystem. While some areas have been converted to rice farms, other areas have gained in mangrove coverage. Overexploitation of mangroves occurs, primarily by external actors, and both local communities and representatives of government authorities ascribe this to lack of financial and human resources to enforce current laws and regulations. Ever since the Rufiji mangrove forest was declared as a forest reserve in 1898, it has been a legal quagmire, with legally established village land within a state forest where human habitation is prohibited by law. This thesis explores management approaches that will embrace conservation with sustainable development. That can only be achieved when local communities are legally recognized as inhabitants and important stakeholders in the conservation of the Delta. A conservation approach that removes land tenure uncertainty among the local communities and takes into consideration the dynamic nature of the Delta must be devised for the Rufiji mangroves.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography, Stockholm University, 2016. 39 p.
Series
Dissertations from the Department of Physical Geography, ISSN 1653-7211 ; 54
National Category
Physical Geography
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-128074 (URN)978-91-7649-389-2 (ISBN)
Public defence
2016-05-13, William-Olssonsalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Sida - Swedish International Development Cooperation Agency
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 2: Manuscript. Paper 3: Manuscript.

Available from: 2016-04-20 Created: 2016-03-17 Last updated: 2016-04-22Bibliographically approved

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