Seagrass Mapping: Kenya

A project led by myself at Edinburgh Napier University with Prof. Mark Huxham and Dr Robert Briers.

Seagrass ecosystems form part of the coastal seascape. They grow on every continent in the world and act as a habitat for a variety of marine ecosystems such as fish and crustaceans. However, these ecosystems are under threat due to rising Anthropogenic pressures and the extent of seagrass coverage has reduced as a result. In East Africa, our knowledge of seagrass spatial coverage is limited and restricted to a few field studies. We set about tackling this knowledge gap by analysing satellite imagery in order to map, for the first time, the spatial coverage of seagrass in Kenya.

Satellite image areas used in the study.

We used Landsat images between 1980 and 2016 to assess changes in seagrass spatial coverage along the coast of Kenya. These were validated with field data of seagrass presence/absence. Below are maps of seagrass coverage for specific locations along the coast of Kenya. As can be seen, seagrass has been lost at all locations; the Watamu-Malindi region in particular has undergone a dramatic decline in seagrass spatial coverage.

Seagrass change at specified locations along the coast of Kenya. Data taken from Harcourt et al. (2018).

The details of this project have been published in Harcourt et al. (2018). The next phase of this project is to implement a management program in Gazi Bay, where a successful Mangrove re-plantation project has been going on for several years (see here). Also, finding the drivers for these changes is also a priority so that management of seagrass ecosystems along the coast can be effectively implemented.

References

Harcourt et al. (2018). The thin(ning) green line? Investigating changes in Kenya’s seagrass coverage, Biol. Lett., 14, doi:10.1098/rsbl.2018.0227.