A Review of Seagrass Cover, Status and Trends in Africa

Abstract

The recognition of the benefits that seagrasses contribute has enhanced the research interest in these marine ecosystems. Seagrasses provide critical goods and services and support the livelihoods of millions of people. Despite this, they are declining around the globe. To conserve these ecosystems, it is necessary to understand their extent and the drivers leading to their loss. However, global seagrass cover estimates are highly uncertain and there are large regional data gaps, especially in the African continent. This work reviewed all available data on the extent of seagrass cover, evidence of changes in cover and drivers of this change in Africa, to inform management and conservation approaches across the continent and identify gaps in knowledge. Using a systematic review and expert consultation, 43 relevant articles were identified. Of the 41 African countries with a coastline, 27% had no data on seagrass cover. For 44%, data were available for some parts of their coastline, while 29% had data for their entire coastline. Quantitative information on trends in seagrass cover change was only available from three countries. The study identified 32 suggested drivers of seagrass cover loss, with impacts from fishing mentioned most frequently. Direct anthropogenic drivers accounted for 66.7% of the mentions, while climate and biologically induced drivers accounted for 22.7% and 10.6%, respectively. This study demonstrates the need for better estimates of seagrass extent, in at least 70% of relevant African nations, and major gaps in our understanding of the drivers of seagrass decline in Africa.

Understanding the drivers of seagrass loss in Kenya: Evidence for the impacts of population and fishing

“…Hence, these results support the frequent reporting of fishing as a major factor in the decline of seagrass across Africa (Mwikamba et al, 2024).…”

“…Only a single paper, reporting on Kenya, contained quantitative estimates of trends in seagrass across the whole country (Harcourt et al, 2018) with Mozambique, Tunisia and South Africa reporting trends in some parts of their coastlines. The most frequently cited potential cause for declines in African seagrass is fishing (Mwikamba et al, 2024). This contrasts with the dominance of eutrophication as the major cause in the global literature but is consistent with anecdotal reports, including observations using remote sensing of geometrical scarring in seagrass beds in Kenya (Harcourt, personal communication), and of large amounts of seagrass being dragged to the surface during fishing activities (Mwikamba, personal observations).…”

“…The status, recent changes, and drivers of change in African seagrass ecosystems are all poorly known. Apart from information from coarse-grained worldwide data sets (McKenzie et al, 2020), there are published data on seagrass extent from only 12 of the 41 African nations with coastlines (Mwikamba et al, 2024). Only one nation (Kenya) has quantitative estimates of change across the whole coastline, and discussion of the causes of any changes in Africa is mostly speculative and based on single sites.…”

“…Research into the possible drivers of seagrass decline in Kenya, or indeed in any African country, is sparse. A recent review found only 43 papers with any data on seagrass extent and/or drivers of change for the whole of Africa (Mwikamba et al, 2024). Only a single paper, reporting on Kenya, contained quantitative estimates of trends in seagrass across the whole country (Harcourt et al, 2018) with Mozambique, Tunisia and South Africa reporting trends in some parts of their coastlines.…”