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MARXAN is a piece of software designed to aid systematic reserve design on conservation planning. With the use of stochastic optimisation routines (Simulated Annealing) it generates spatial reserve systems that achieve particular biodiversity representation goals with reasonable optimality.

Computationally, MARXAN provides solutions to a conservation version of the 0-1 knapsack problem, where the objects of interest are potential reserve sites with given biological attributes. The simulated annealing algorithm attempts to minimise the total cost of the reserve system, while achieving a set of conservation goals (typically that a certain percentage of each geographical/biological feature is represented by the reserve system).

Contents 1 History 2 Application 3 Shortcomings 4 References 5 External links

MARXAN is a portmanteau acronym, fusing MARine, and SPEXAN, itself an acronymn for SPatially EXplicit ANnealing. It was a product of Ian Ball's PhD thesis, while he was a student at the University of Adelaide in 2000, and was supervised and funded by Hugh Possingham, who currently holds a Federation Fellowship at the University of Queensland. It was an extension of the existing SPEXAN program.

MARXAN is the most widely used systematic reserve planning software in the world ^[1], and has most famously been used to create the marine reserve network on the Great Barrier Reef, in Queensland, Australia, the largest marine protected area on the planet ^[2]. It has been used for many other marine reserve planning applications, including:

• Florida Keys [1]
• Channel Islands of California ^[3]
• Gulf of Mexico [2]
• Galapagos Islands
• South Australia [3]
• British Columbia
• Connecticut/New York
• Central Coast of California

(For more details of these applications, go to the Ecology Centre MARXAN Homepage)

MARXAN has been used extensively by The Nature Conservancy (e.g., their Carolinan Marine Ecosystem Assessment), and is a major part of the systematic planning tools being used in the Global Marine Initiative. The World Wildlife Fund used MARXAN to define a Global set of Marine Protected Areas, the Roadmap to Recovery, which they used to petition the UN about the creation of open ocean marine reserve networks.

The software has also been used in terrestrial applications, such as:

• The North American Wildlands Project.
• Selecting priority areas for Global Mammal Assemblages ^[4].

One shortcoming of MARXAN is its inability to deal with issues of demographic inter-connectedness. In marine systems, the presence of a biological feature does not guarantee the persistence of that feature in the absence of the surrounding ecosystem. This is a concept generally known as "connectivity". MARXAN considers that including into a reserve system a site that contains a particular feature will ensure the persistence of that feature, even though surrounding sites may not be included in the reserve system, and may therefore be ecologically compromised. MARXAN does employ a "boundary length modifier", which attempts to minimise the boundary length to area ratio, thus increasing the continuity of the reserve systems. This ad-hoc alteration may go some way to addressing the problem ^[5].

• MARXAN Homepage, information and download
• A thorough rundown of the software specifications by the National Commission on Science for Sustainable Forestry
• This article in Marine Protected Area News discusses the pros and cons of the software in the context of MPA planning.