Chapter 1: The state of our blue planet page 150121970 1980 1990 2000 2010Index value (1970=1)YearFigure 11: The index
for fish in seagrass
habitats shows a
decline of over 70 per
cent between 1970 and
2010 (WWF-ZSL, 2015).
Key
Seagrass-associated
fish index
Confidence limitsZSL calculated an index for fish populations found in seagrass
habitats, based on data on 350 populations of 232 species. This
shows a dramatic decline of over 70 per cent between 1970 and 2010
(Figure 11). LPI data sources identify exploitation as the main threat
to populations in seagrass habitats, followed by habitat degradation/
change; the threat of pollution appears to be higher within seagrass
habitats than in the indices for fish and coral reefs discussed above
(WWF-ZSL, 2015).Mangroves
Mangroves are known to exist in 123 countries, though just five
(Indonesia, Australia, Brazil, Nigeria and Mexico) account for
almost half (45.7 per cent) of the total global mangrove area
(Spalding et al., 2010). They provide spawning grounds, nurseries,
nutrients and shelter for many species, including fish, reptiles,
amphibians, mammals and birds (Nagelkerken et al. 2008).
They also provide a variety of benefits to human populations,
including provisioning services (firewood, timber, fisheries, other
forest products), regulating services (coastal protection, carbon
sequestration, buffering seagrass beds from terrestrial sediment/
nutrient loads), and cultural services (recreation, ecotourism,
spiritual) (UNEP, 2014).
Worldwide, nearly 20 per cent of mangrove cover was
lost between 1980 (18,794,000 hectares) and 2005 (15,231,
hectares), equal to nearly 3.6 million hectares (Figure 12). The
primary cause of this loss was the conversion of mangrove areas to
different uses such as aquaculture, agriculture, infrastructure and
tourism, as a result of increasingly high human population pressure
in coastal areas (FAO, 2007).