In recent decades protection of the environment has become an issue of wide public interest. Both on a national and an EU level a multitude of statutes and directives in this area have been enacted. In many cases, these provisions intervene into business activity. This paper explores the way in which environmental protection law can affect real estate projects. The paper uses the example of a development project in Hamburg/Germany, where a population of corncrakes (a small bird) halted a large scale housing project as the bird is protected under the EU Birds Directive (79/409/EEC). The author conducts a cost benefit analysis (CBA), comparing the stopped project and a newly proposed, amended project, which takes the requirements of the directive into account. The author reviews as to whether a study of this nature is justified under aspects of philosophy of science and as to whether the employed method of cost-benefit analysis is appropriate for this purpose By using the residual value method of land valuation the author determines the implicit value which society places on a corncrake. This value is defined as the difference between the residual land value of the stopped project and the residual land value of the alternative project. The value of the bird is thus expressed as the foregone profits which could have been realised with the first, much larger project. The result is that society’s valuation of a corncrake amounts to approximately Euro7.2m. A sensitivity analysis and discussion of limitations conclude the paper.