In recent years it became clear that humans have a significant impact on our planet. The publicly most discussed topics in this regard are climate change and conservation, two topics that are not independent, e.g. forests act as carbon sinks but become more vulnerable to pests in a warmer climate. Together with increased land use by humans more and more habitat for native species is lost. In addition a globalized economy frequently introduces invasive species that compete with the native species. These effects combined lead to extinction rates that are currently estimated to be orders of magnitude higher than the background rate .
To counter this global extinction event many efforts have been taken to save species. But the question always arises why one should bother to do so. The answers are varied and range from ethical reasons (other species have the right to live) to economical considerations (some plant might hold the next “cure for cancer”). Even if one has come to the conclusion that the extinction of species should be averted it is not clear what policies would be effective in doing that. In a free market economy it might seem best to use economic incentives to create a demand for sustainably managed landscapes.
One way to use arguments from economics to justify conservation efforts are ecosystem services, a term popularized by a 2005 United Nations report . Ecosystem services describe the processes that nature provides to human societies for free. For example plants provide oxygen, filter water and stabilize the ground using their roots, and provide shade. Another, more prominent example, are bees pollinating crops.
Calculating how much it would cost to replace these services gives an economic incentive to preserve functioning ecosystems. As ecosystems can function best if as many of their original species as possible survive the preservation of individual ecosystem services can save many species .
The study of ecosystem services does not only highlight the economic importance and the biodiversity gain but it also demonstrate how dependent humans are on their environment.
While the cost of single ecosystems services can be calculated  it is difficult to estimate what the costs would be on a larger scale. It is also not clear if an artificial replacement for all such services could be implemented in practice. The question of how much it would cost to replace destroyed ecosystem is thus still open.
 Pereira et al., “Scenarios for Global Biodiversity in the 21st Century”, Science 330, 1496 (2010)
 Mace, Norris & Fitter, “Biodiversity and ecosystem services: a multilayered relationship”, Trends in Ecology and Evolution 27, 19 (2012)
 Chichilnisky & Heal,“Economic returns from the biosphere ”, Nature 391, 629 (1998)