Facilitating Mangrove Restoration through Technology

Facilitating Mangrove Restoration through Technology
March 15, 2018 10:45 am Blog

New remote sensing data on mangrove coverage can inform mangrove restoration efforts in coastal West Africa: A Sierra Leone Case Study.

Developing countries are the most vulnerable to the effects of climate change. In countries with coastal communities, severe flooding and coastal erosion are two of many effects climate change could wreak over the coming years, if not addressed. Mangroves have proven to be useful in reducing these negative impacts significantly when planted along the shorelines by acting as coastal barriers. However, many coastal communities in Africa use mangrove trees for benefits other than protection from floods and soil erosion. In coastal communities in Sierra Leone for example, mangroves are cut down to smoke fish and to make way for cultivation of other food crops. The effects of climate change, compounded by unsustainable practices and declining mangrove populations, are posing a serious risk to the lives, livelihoods, and property of coastal communities. Some are already experiencing increased flooding, underscoring the urgent need to restore these mangroves.

Decadal changes in mangrove extents in the Sierra Leone Coastal Landscape complex.
Decadal changes in mangrove extents in the Sierra Leone Coastal Landscape complex.

 

To restore mangroves, there must first be a data-backed understanding of the extent to which these mangroves’ populations have changed over time. This data is often difficult to obtain on the ground, especially when accessibility to the area is poor. In recent years, advanced technology has made it possible to bypass some of these challenges. Researchers can now use remote sensing technology to collect data via satellites. A team of researchers from the Center for International Earth Science Information Network (CIESIN) at Columbia University (USA), a partner to WA BiCC, used Landsat satellite data and Google Earth to analyze coastal mangroves in the Sierra Leone Coastal Landscape and showed 95% accuracy when compared to pre-existing data. This was a first attempt to provide detailed estimates of changes in mangrove extents over time (1990-2016). Progress of mangrove restoration can also be monitored easily using this method.

Relative extents of different land covers within the four focus areas during 1990–2016. Panels show mangrove extents within buffers of (a) 1 km, (b) 2.5 km, (c) 5 km extending inland from the coastline.
Relative extents of different land covers within the four focus areas during 1990–2016. Panels show mangrove extents within buffers of (a) 1 km, (b) 2.5 km, (c) 5 km extending inland from the coastline.

 

This is great news for conservation experts, as remote sensing data can fill many data gaps and inform decisions and activities in the field. For instance, the data can tell us where mangrove deforestation is happening most rapidly and requires immediate attention. Based on the findings of this research, WA BiCC has started a pilot project to restore and improve the management of 1000 hectares of degraded mangrove land in all the four coastal regions of Sierra Leone is currently in progress, thanks to findings from this research. This project will provide essential lessons to complement the satellite data in future instances. Information will also be shared with partners and other development agencies to scale up mangrove restoration in Sierra Leone and West Africa.

Maps from Google Earth Engine showing Landsat footprints covering Sierra Leone; and location of validation points.
Maps from Google Earth Engine showing Landsat footprints covering Sierra Leone; and location of validation points.

 

A detailed report on the method and results used in the research can be found in this article titled “Landsat-derived estimates of mangrove extents in the Sierra Leone Coastal Landscape Complex during 1990-2016

 

Story developed by Zebedee Njisuh and Edudzi Nyomi 





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