By Benedetta Wasonga

Most of Kenya is arid, and lengthy droughts can lead to livestock loss, illegal grazing in protected areas, and violent interactions between nomadic herders and other landowners. Less known are its forests, located along its coast and along Lake Victoria that are humid and often covered by clouds.

Using Sentinel-1 radar imagery, Forest 2020 project Manager Mr. Jamleck Ndambiri says they are now able to map these previously hard-to-assess forests at the coastal region through a combination of satellite data acquisition and verification, processing and ground-truthing that can now help Kenya assess and monitor our national forest cover more accurately and timely.

“But there were data gaps.”

Historically, the Kenyan government depended on expensive and time-consuming ground surveys to assess and undertake inventory its forests. Between 2011 and 2013, the country engaged in its first-ever national forest mapping effort using satellite imaging technology, with funding from the Japanese government.

The project first trained local personnel from several relevant institutions and disciplines to use the new computing technologies and established a national Geographic Information System (GIS) lab and human capacity on data analysts combined Landsat images from 1990 to 2000 with images from the Japanese Advanced Land Observing Satellite (ALOS) from 2000 through 2010 to assess the extent of Kenya’s forests and changes in land cover over the 20-year period between 1990 and 2010.

Parts of Kenya, particularly the coastal and western regions, experience persistent cloud cover for most of the year, due to their proximity to the Indian Ocean and Lake Victoria water bodies, respectively. Clouds present a barrier to light-dependent optical imaging satellites, such as Landsat, and Forest 2020 project was to test and adopt “cloudless imagery,” or radar to provide more accurately maps devoid of cloud within the cloudy forest regions.

A 2013 study led by Kenya Marine and Fisheries Institute (KMFRI) that analyzed the Landsat data estimated that Kenya has 590 square kilometers of mangrove forests along the coastal strip. The study estimated that 18 percent of the mangrove forest was lost during the 25 years to 2010. However, the high frequency of clouds in the coastal areas and the medium (30-meter, or 98-foot) resolution of the Landsat imagery used to analyze the complicated coastline may have caused the analysis to underestimate the area of coastal mangroves.

Other official documents indicate significant differences in mangrove forest cover. A 10-year National Mangrove Ecosystem Management plan proposal by Ministry of Environment and Forestry, which includes KFS, the mangrove forest cover at 613 square kilometers.



Mangroves protect coastal ecosystems against soil erosion and extreme weather. Their deep root systems serve as nursery grounds for fish, shrimp and crabs, and their canopies provide nesting grounds for birds.


In Kenya rapid population growth, urbanization and climate change, have posed new challenges to livelihoods along the 600-kilometer (373-mile) coastline and that these events have exacerbated resource exploitation, especially of the area’s sensitive mangrove forests.

Radar to fill data gaps for cloudy areas.

To address these gaps, Forest2020 project in 2017 funded through Ecometrica a private company dealing with software development for satellite image processing and UK Space agency was conceptualized and aims to help protect and restore tropical forests by improving forest monitoring in Kenya through the use of satellite data. Forest2020 also works in Ghana, Indonesia, Brazil, Colombia and Mexico.

The universities of Leicester and Edinburg in the UK provide technical assistance to the project. Locally, KFS is collaborating with Kenya Forestry Research Institute and Jomo Kenyatta University of Agriculture and Technology, both public institutions. The collaboration has allowed for wider transfer of knowledge for the new data collection, analyzing, processing and management technologies.

With these requirements, especially for mapping coastal forests, the Forest2020 team acquired high resolution image data from the Synthetic Aperture Radar (Sentinel-1) satellite. Sentinel-1 is one of two weather- and daylight-independent radar satellites launched by the European Space Agency in 2014. The Sentinel-1 project, which focuses on land and ocean monitoring, provides a constant supply of free, 10-meter (66-foot) resolution radar data for the entire planet.

The Kenya Forest mapping project targets 2,039 square kilometers (787 square miles) of Kwale County, one of six counties in the coastal region, which together cover about 80,000 square kilometers (30,888 square miles). “This is a pilot run to develop a competent methodology that, if successful, could be replicated in the whole coastal region and other areas with persistent cloud cover.

The project team acquired and processed Sentinel-1 images for the prescribed area during September and October 2017, applying various data processing algorithms to classify the Kwale vegetation and land uses. To resolve persistent misclassifications, such as between mangroves and terrestrial forests, the team used DT – Decision Tree software.

With a draft map in hand showing the land use patterns across Kwale County human settlements, grasslands, farmlands, water bodies and forest types, this involved verifying whether the classifications in the draft map showed what was actually on the ground verification to assess accuracy of the draft land cover map and ascertained the map was about 75 percent accurate which after verification accuracy improved to 85 percent.


Applying radar data across forest types

Poor internet connectivity and slow downloads times sometimes hindered work to map these forests in detail, as did regular power outages, which are not unusual in the country.

Despite the operational challenges, “this is the first time actual mapping of mangrove forest has been done in Kenya at such a micro scale and have produced a very detailed maps of the target area, which we will soon share with our implementing stakeholders.

The project’s land use data shows increasing human settlement and forest use, which threatens fragile coastal forests despite their economic and environmental benefits. For example, in areas showing either receding or recovering mangroves, KFS will alert local forest officers and communities to take necessary measures and the Project plans to map the rest of the coastal forests between now and next year and share the findings with local communities through KFS relevant offices.

Other activities being done by the project include an ongoing biomass pilot study of Kenya’s dryland forests and levels of degradation in the 1,200 square-kilometer (463 square-mile) Cherangani forest in the Rift Valley.

KFS expects to roll out the tool for use at a national scale for forest and biomass monitoring. Current estimates show Kenya’s land area is roughly seven percent forest cover, against its target of 10 percent. Once KFS has mapped the forests in cloud-persistent and dryland forest areas, KFS will have a more accurate estimate of the national forest cover for future analyses.




     Mangroove Forest in Mtwapa, Mombasa County.


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