There is growing evidence that seagrasses are experiencing
declines globally due to anthropogenic
threats (Short and Wyllie-Echeverria 1996, Duarte
2002, Orth et al. 2006). Runoff of nutrients and
sediments that affect water quality is the greatest
anthropogenic threat to seagrass meadows,
although other stressors include aquaculture, pollution,
boating, construction, dredging and landfill
activities, and destructive fishing practices. Natural
disturbances such as storms and floods can
also cause adverse effects. Potential threats from
climate change include rising sea levels, changing
tidal regimes, UV radiation damage, sediment
hypoxia and anoxia, increases in sea temperatures
and increased storm and flooding events.
Thus, seagrass meadows, the ecosystems that
they support and the ecosystem services that they
provide are threatened by a multitude of environmental
factors that are currently changing or will
change in the future.
Seagrasses are flowering plants that thrive in shallow
oceanic and estuarine waters around the world.
Descendants of terrestrial plants that re-entered
the ocean between 100 and 65 million years ago,
seagrasses have leaves, stems, rhizomes (horizontal
underground runners) and roots. Although
there are only about 60 species of seagrassesworldwide, these plants play an important role in
many shallow, near-shore, marine ecosystems.
Seagrass meadows provide ecosystem services
that rank among the highest of all ecosystems on
earth. The direct monetary outputs are substantial
since highly valued commercial catches such
as prawns and fish are dependent on these systems.
Seagrasses provide protective shelter for
many animals, including fish, and can also be a
direct food source for manatees and dugongs,
turtles, water fowl, some herbivorous fish and sea
urchins. The roots and rhizomes of seagrasses
also stabilise sediments and prevent erosion while
the leaves filter suspended sediments and nutrients
from the water column. Seagrass meadows
are thus linked to other important marine habitats
such as coral reefs, mangroves, salt marshes and
This paper presents an overview of seagrasses,
the impacts of climate change and other threats to
seagrass habitats, as well as tools and strategies
for managers to help support seagrass resilience.
IUCN, Gland, Switzerland , 2008. , 56 p.