Larger MPAs generally cost less to manage per unit area than smaller ones, and no-take areas are cheaper to manage than multiple-use MPAs, according to a study by an Australian research team, published in the journal Conservation Letters. The study estimated the management costs of two scenarios for a potential MPA in Australia’s Coral Sea: one a single large no-take area, the other a multi-use MPA of which nearly one third was no-take.

The bottom line: annually, it would cost 70% more to manage a large multiple-use MPA than to manage a no-take area of the same size, according to the team’s estimates. This is primarily due to the costs of compliance and enforcement, they write. In short, the zoning in a multi-use area makes compliance more challenging, leading to more offenses and an increased need for monitoring and enforcement activity.

Led by Natalie Ban of James Cook University, the research team used three models to estimate costs: an existing model of global MPA management costs, a new statistical model based on Australian MPA management costs, and expert estimates derived from the management costs of the adjacent Great Barrier Reef Marine Park.

The findings are relevant to current Australian policy-making. The Australian Government has designated the country’s portion of the Coral Sea as a Conservation Zone for interim protection, and is assessing its possible inclusion in one or more Commonwealth MPAs. The Coral Sea Conservation Zone covers approximately 972,000 km2 of Australian waters. Some conservation groups, like Pew Environment Group, are advocating 100% no-take coverage for the entire area, whereas a 30% no-take scenario would more closely approximate the no-take coverage of the Great Barrier Reef Marine Park.

An intriguing finding from the study: once an MPA reaches a very large size, its per-unit management cost may start increasing again. Natalie Ban spoke with MPA News about this phenomenon and her study’s findings in general:

MPA News: You focused your calculations on one case: a Coral Sea MPA. Can your findings be generalized to MPAs elsewhere in Australia and the world?

Natalie Ban: Our estimates of management costs for protection scenarios of the proposed Coral Sea MPA were based on budget data from Australian Commonwealth MPAs and expert interviews. The expert interviews were specific to the Coral Sea, but the statistical model we used to estimate management costs is applicable to small and large MPAs elsewhere in Australia. We do not know whether Australian data reflect global patterns of management costs.

MPA News: You found that management costs per unit area generally decrease as an MPA increases in size. However, you also determined that in the case of very large MPAs, a certain threshold size is reached where management cost per unit area actually starts to increase again. You refer to this rebounding trajectory in cost as a “polynomial relationship”. Can you explain this?

Ban: It makes sense that the per-unit management cost cannot decline indefinitely for really large MPAs, because then it would cost essentially nothing to manage these areas. We know this cannot be true.

Here is one way of thinking about the scale issue. Enforcement effort can stay relatively constant until an MPA or network of MPAs reaches a certain area. A single vessel is required for one small MPA and might also be adequate for two small MPAs, although 1.5 times the vessel time could be required. If a single medium-sized MPA is configured to encompass the two smaller MPAs and additional waters, a single vessel could still be sufficient because the distance traveled is the same and there is less perimeter to patrol, resulting in a decreased per-unit-area cost and displaying an economy of scale. The same economies of scale might not hold when an MPA reaches a threshold area. If the MPA becomes very large, two vessels could be required to effectively patrol the perimeter, increasing management costs for compliance in absolute and per-unit-area terms. The additional vessel is an example of a stepped fixed cost. Together with variable costs (e.g., fuel, staff time), this would translate into the kind of polynomial relationship that we found for Australia between management costs per unit area and total area.

MPA News: In your view, does that polynomial relationship provide an argument against establishing really large MPAs?

Ban: Many factors in addition to management cost are important to consider when assessing potential sizes and configurations of MPAs. When considering only management cost, it would still be more cost-effective to have one large than two smaller MPAs, because it is so much more expensive per unit area to manage smaller areas.

MPA News: Earlier this year, a team at the University of British Columbia in Canada published a study analyzing the cost of establishing MPAs, as opposed to managing them (“Understanding the cost of establishing marine protected areas”, McCrea-Strub et al., Marine Policy 35[1], 1-9). How do your findings compare to theirs?

Ban: Their findings were similar to ours in that they also found that larger areas are cheaper to establish per unit area than small ones. However, they did not find a polynomial relationship, and thus their study suggests that establishment costs are less per unit area even for extremely large MPAs, such as our Coral Sea scenarios. A polynomial relationship between size and cost might not be expected in establishment costs because they may be comprised predominantly of fixed costs that are not tied to the size of the MPA. For example, the quantity of staff and software needed for the planning phase of a marine park may be the same regardless of the size of the planning region, therefore resulting in a linear decreasing per-unit establishment cost as a function of MPA size. However, their study nicely complements ours, because both establishment and management costs are important to think about at the beginning of an MPA planning process.

For more information:

Natalie Ban, Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia. E-mail:

“Promise and problems for estimating management costs of marine protected areas” appears in Conservation Letters (2011) 1-12. For a copy, e-mail Natalie Ban at the address above.