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

Abstract

Seagrass ecosystems are crucial for supporting biodiversity and serve as vital fishing grounds. Unfortunately, their cover is declining globally. In Kenya, seagrass cover is falling by ~ 1.6% annually but the causes are unknown. This study investigated the possible anthropogenic drivers of seagrass decline along the Kenyan coastline. Satellite and large-scale geographic data on population growth, chlorophyll α trends, housing, and road density were used to explore their effects on seagrass cover loss along the whole coastline. Direct investigations were conducted into the effects of seine netting and basket trapping within seagrasses. There was an average loss of 1.9 km2 per 25 km2 seagrass cover between 2000 and 2016 and a weak but significant relationship between population growth and seagrass decline, with losses concentrated in areas with the highest population density. In contrast with studies elsewhere, there was no evidence implicating eutrophication, supporting the suggestion that declines are linked to direct anthropogenic impacts such as fishing. A field experiment showed that a single instance of seine netting caused a significant loss of seagrass cover of 8.3% within the area fished, while no significant changes were observed with basket traps. These findings support the evidence that declines in seagrass in Kenya and in other African countries are anthropogenic and are linked with fishing pressure and endorse existing efforts to restrict use of seine netting within seagrasses. Understanding the status, changes, and drivers of change in seagrass ecosystems in Africa is crucial for developing effective national and local seagrass conservation plans, and for compliance with international commitments on seagrass conservation.