progressive 0–100% reduction in extent of coral cover will have
on reef community structure, and the effect of these changes on
fishery production (see Box 1). This study demonstrates how reef
degradation will affect reef fishery production, and thus local livelihoods and the national economy.
2.3. Identifying priority areas for application of systematic MSP
As a first approximation for identifying priorities for immediate
management response, we constructed a simple model that ranks
areas according to cumulative pressures and potential user con-
flicts. To approximate the intensity of human impacts on tropical
coastal seas around the world we used the ‘focalmean’ tool in
ArcCatalog to extrapolate a population proximity index for each
of the grid cells in the continental shelf region of the tropics.
‘Focalmean’ calculates a new value for each grid cell in an existing
grid, based on the value of surrounding grid cells. For our analyses,
we used a circular region around each grid cell, which extended
out to a radius of 100 grid cells. This approximated a focal mean
radius of about 93 km at the equator. We created a source grid
for our focal mean calculations by combining the LandScan grid
with the continental shelf grid. Each of the grid cells in the shelf
region of the source grid had a value of 0, and all of the terrestrial
grid cells had the corresponding population count information
from LandScan. We masked out all land grid cells in the resulting