The effects of human population density on coral reef fish

By Brittany Bartlett, RJD Intern

Coral reef fisheries are extremely important to the livelihoods of millions of people. Unfortunately, habitat degradation and unsustainable fishing practices have resulted in a decline in these fisheries. Therefore, a recently published article by T.D Brewer et al. entitled “Effects of Human Population Density and Proximity to Markets on Coral Reef Fishes Vulnerable to Extinction by Fishing” seeks to understand the social and economic issues behind this depletion in order to improve management.

Oftentimes, the fundamental drivers of resource depletion tend to be overlooked. Therefore, Brewer examines three distal drivers (human population density, access to external markets, and modernization) and two proximate drivers (fishing with basic gear and efficient gear, and habitat) in order to determine how these factors intermingle with fishing and habitat degradation to affect fish populations. Past research has come to three conclusions regarding environmental/human interactions: 1) human demography affects natural resource abundance (an increase in human population results in a decrease in natural resources), 2) local resource decline results from exportation through markets (the condition of a fishery correlates with the distance from a market), and 3) modernization affects how resources are used. Prior to this paper, however, no study had examined these three hypotheses simultaneously in attempts to explain the distribution of various vulnerable species to human activities.

from Brewer et al. 2012

The study was conducted in the Solomon Islands. Here, 90% of the population eats reef fish. The population is rapidly growing by 2.8% per year and gradual modernization is occurring. Vulnerability of fish species was classified as high, low, or medium. The three potential distal drivers were assessed as follows: human population density as the total number of inhabitants within the boundary of each site per coral reef area, market proximity as the shortest distance from the center of each ecological sample location to the center of the nearest local fish market and modernization as the sum of the set of weighted infrastructures and amenities with site boundaries.

Distal drivers (population density, market proximity, modernization) determined much of the differences among the proximate drivers (fishing with basic and/or efficient gear and habitat). The 3 distal drivers explained 76% of the variance of efficient gear fishing, modernization and population density explained 82% of the variance of basic fishing gear, and modernization, population density and efficient gear explained 33% of the variance of coral cover. Thus, the distal drivers were good predictors of fishing intensity, but not coral cover.

From Brewer et al. 2012

Conservation management is dependent on a wide variety of complex factors. Understanding these distal and proximate drivers allows us to better understand and, thus address, the causes of fishery depletion.

REFERENCE:

Brewer, TD et. al. (2012) “Effects of Human Population Density and Proximity to Markets on Coral Reef Fishes Vulnerable to Extinction by Fishing” Conservation Biology.