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.
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.
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. Documenting these changes is vital in order to understand the drivers of seagrass loss. We have suggested that fishing damage is one of the primary causes of change along the Kenyan coast, but other Anthropogenic influences (e.g. land-use practices) are likely to be important.
These data sets also form the basis of analysis for other projects. For example, we are using the seagrass coverage maps to analyse fish movement around the reef ecosystems of Southern Kenya.
Harcourt, W.D., Briers, R.A., Huxham, M. (2018). The thin(ning) green line? Investigating changes in Kenya’s seagrass coverage, Biol. Lett., 14, doi:10.1098/rsbl.2018.0227.