Software for prioritizing conservation actions based on probabilistic information4.

Marxan is the most commonly used decision support tool for informing the design of protected area systems. There is a great deal of risk and uncertainty associated with the outcome of protected area decisions that the original version of Marxan does not consider, including uncertainty about the location and condition of species populations and habitats now and in the future, given threatening processes. The functionality of a modified version of Marxan, Marxan with Probability, is described here. It is able to explicitly consider four types of uncertainty, the: 1) Probability that a feature exists in a particular place, estimated with species distribution models or spatially explicit population models; 2) Probability that features in a site are lost in the future due to a threatening process, such as climate change, natural catastrophes or uncontrolled human interventions; 3) Probability that a feature exists in the future due to natural successional processes, such as a fire or flood disturbance; 4) Probability the feature exists but is degraded by threatening processes and cannot contribute towards conservation goals, such as overfished or polluted marine ecosystems. We summarize five studies that illustrate how each type of uncertainty can be used to inform protected area design. This version of Marxan opens up substantial new avenues of systematic conservation planning research and application by agencies for delivering protected area systems on the ground. This article is protected by copyright. All rights reserved.