ingly use ecological data alongside social and
economic information to guide the design of
MPAs. But marine connectivity is “still the
new kid on the block.”
Metaxas and Dalhousie University
graduate student Arieanna Balbar recently
reviewed nearly 750 M PA s in regions of
the globe with advanced conservation ini-
tiatives. They found that just 11 percent
included considerations of marine con-
nectivity, and most of those that did were
in Australia and California, which have
the largest and second-largest networks of
MPAs, respectively.^10 New research guide-
lines take a while to trickle down into man-
agement plans, Metaxas says, and there’s
still a lack of data for many of the marine
areas that policymakers want to protect.
“ Yo u have a disconnect between what man-
agers can do and what scientists write in
the literature that they should do.”
To help conservation planners con-
sider marine connectivity even when data
are sparse, Carr and others have promoted
the idea of “rules of thumb” to guide the size
and spacing of individual M PA s within a
larger network of protected areas. Accord-
ing to these rules, developed in California
after the state passed the 1999 Marine Life
Protection Act, each M PA should have an
area of at least 50 square kilometers—large
enough to contain all of the adults in most
local reef or coastal fish populations. Fur-
thermore, M PA s should be spaced closely
enough that larvae from one M PA can dis-
perse to an adjacent one—ideally, a distance
of no more than 100 kilometers.California’s M PA network is consid-
ered a model example, says Carr, and
other managers, such as those in Oregon,
have based their own marine protection
plans on a similar framework. (See “Pro-
tected Area” on opposite page.) Ye t some
researchers argue that rules-of-thumbapproaches risk oversimplifying connec-
tivity by ignoring factors specific to indi-
vidual species or regions, and overlooking
empirical data that may be on hand.
Metaxas and undergrad student Jenny
Smith recently developed a decision tree
that tries to incorporate more of that local
specificity by walking conservation planners
through a series of connectivity-relevant
questions about a target species or habi-
tat.^11 For example, according to the tree, a
species with larvae that disperse over short
distances would likely require that M PA s be
large enough to capture that dispersal and
ensure each population is adequately pro-
tected locally, but the spacing of the M PA s
may not matter if dispersal outside the region
is rare. The approach helps planners identify
the aspects of marine connectivity that are
most relevant and weigh them against other
factors guiding M PA design—from ecologi-
cal considerations such as a region’s existing
biodiversity to socioeconomic factors such
as the income and livelihoods of local fish-
ermen, says Metaxas. Connectivity “may not
always be necessary to include,” she explains.
“But it should always be considered.”
Efforts to design effective networks of
M PA s are made particularly tough by theConnectivity may not
always be necessary
to include. But it
should always be
considered.
—Anna Metaxas, Dalhousie UniversityTHE LANGUAGE OF THE SEA
A relatively young concept in marine biology, marine connectivity is loosely defined as the exchange of indi-
vidual organisms, food, or other material between habitats or populations in the ocean. In addition to this
umbrella term, researchers also use several non-mutually-exclusive subtypes of marine connectivity to
describe species’ patterns. These terms have equivalents in research on connectivity in terrestrial habitats, too.
STRUCTURAL CONNECTIVITY
Movement due to the physical
characteristics of the environment.
Ocean currents and seafloor topography
help determine structural connectivity.DEMOGRAPHIC CONNECTIVITY
The effect of individuals’ movement
on the size, growth, and other
characteristics of a population.GENETIC CONNECTIVITY
The effect of gene flow on evolutionary
processes in a population.FUNCTIONAL CONNECTIVITY
Movement due to the ecological traits
of an organism. Dispersal ability plus
habitat and food preferences influence
functional connectivity. THE SCIENTISTSTAFF