Living Blue Planet Report

Living Blue Planet Report page 14

Figure 10: Net area of

seagrass gain and loss

per decade in study

sites^ (Waycott et al.,

2009).

1930s

nd

nd

pre-1930 1940s1950s1960s1970s1980s1990s2000s

120

80

40

0

Number of sites

0

5

10

15

• 
  


• 
  

  Median rate of change (μ, % y-

  
  

-1)

200

100

0

Net change in area (km2)

Key

Decreasing

No detectable change

Increasing

Seagrass
Seagrass meadows provide a range of ecosystem services, from
catching sediment and stabilizing the seabed (Gillis et al., 2014)
to providing grazing for dugongs, manatees and green turtles, and
critical habitat for commercially important fish species (Orth et
al., 2006). They also store vast amounts of carbon: Fourqurean et
al. (2012) estimate that seagrass meadows store 83,000 tonnes of
carbon per square kilometre, more than twice as much as a typical
terrestrial forest.
Seagrass coverage worldwide has declined by about 30 per
cent over the last century. Waycott et al. (2009) carried out a
global assessment of 215 studies to determine the status of seagrass
habitats. A total of 1,128 observations from around the world
between 1879 and 2006 were included in their assessment, which
indicated a mean decline in seagrass area of 1.5 per cent per year,
adding up to a total of 3,370km^2 lost in 127 years on those sites
(Figure 10).
Extrapolating these figures to a global scale suggests that
more than 51,000km^2 of seagrass meadows have been lost since
1879, a total of 29 per cent of seagrass area. The current global
estimate of seagrass coverage is 177,000km^2 (Waycott et al., 2009).