Government and non-government conservation agencies have long-term goals and objectives to provide environmental services, such as conserving the biodiversity of Australian native vegetation. In addition to national parks and reserves, private lands are often included in conservation programs to achieve these objectives. Formal contracts are entered into between the private landholder and the conservation agency to provide environmental services, or more commonly to provide inputs that are likely to lead to environmental services. The paper examines the costs and benefits of monitoring these conservation contracts when biodiversity change is stochastic.