Protecting large, isolated areas of no-take
zones for over 10 years with strong enforcement is the key to effective Marine
Protected Areas (MPAs), according to a letter published this week in Nature.
However, 59% of all MPAs meet less than three of the five criteria, making them
protected in name only.
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… to
The authors look at 964 sites in 87 MPAs
worldwide and identify which factors determine a successful MPA. They write
that the key ingredients are: “(1) degree of fishing permitted; (2) level
of enforcement; (3) MPA age; (4) MPA size; and (5) presence of continuous
habitat allowing unconstrained movement of fish.” An MPA that fails to
meet at least three of these criteria is statistically no different from fished
areas, while each additional factor above three increases its conservation
value exponentially.
Although the authors do find that, “across
all 87 MPAs investigated, species richness of large fishes was 36% greater
inside MPAs compared to fished areas, biomass of large fishes was 35% greater,
and sharks 101% greater,” they continue to note that, “for species
richness of all fishes and the other four bio- mass metrics investigated, no
significant difference was found.”
The poor overall performance of MPAs worldwide
is likely due the significant number of ineffective protected areas: only four
of the 87 MPAs studied meet all five key criteria. Using those
“effective” Areas as a standard, the authors find that in the other
MPAs, “fish biomass was greatly reduced overall, with 63% of all fish
biomass, 80% of large fish biomass, 93% of sharks, 84% of groupers and 85% of
jacks apparently removed from reefs by fishing.”
MPAs have proliferated in recent years as
countries rush to meet protection targets. In 1970, there were 118 MPAs in 27
nations. By 1994, over 1,300 MPAs existed worldwide. In 2010, nearly 5,900 MPAs
had been established. However, as impressive as those numbers sound, protected
areas account for less than 2% of the world’s oceans, and without effective
management, do little to assist in recovery of diversity or biomass.
There is no single factor that determines the
success of an MPA, however, size and isolation appear to be most favorable for
large species such as sharks and groupers. In the absence of size, the additive
effect the other four factors—effective management, enforced no-take policies,
long-term establishment, and inclusion of deep-water areas surrounding
reefs—can be sufficient to compensate.
Read more at ENN affiliate Mongabay.
MPA map via the Marine
Conservation Institute.