Just setting up nature reserves will not be enough...

[auroraglacialis]

Ongoing global biodiversity loss unstoppable with protected areas alone

Despite impressively rapid growth of protected land and marine areas worldwide -- today totalling over 100,000 in number and covering 17 million square kilometers of land and 2 million square kilometers of oceans -- biodiversity is in steep decline.

Expected scenarios of human population growth and consumption levels indicate that cumulative human demands will impose an unsustainable toll on Earth's ecological resources and services accelerating the rate at which biodiversity is being loss.

"Ongoing biodiversity loss and its consequences for humanity's welfare are of great concern and have prompted strong calls for expanding the use of protected areas as a remedy," says fellow author Peter F. Sale, Assistant Director of the United Nations University's Canadian-based Institute for Water, Environment and Health.

"While many protected areas have helped preserve some species at local scales, promotion of this strategy as a global solution to biodiversity loss, and the advocacy of protection for specific proportions of habitats, have occurred without adequate assessment of their potential effectiveness in achieving the goal."

Drs. Mora and Sale warn that long-term failure of the protected areas strategy could erode public and political support for biodiversity conservation and that the disproportionate allocation of available resources and human capital into this strategy precludes the development of more effective approaches.

Read the full article for more - also take a look at the graph.
BAsically the reason this is not working is, that the protected areas are only local, migrations are impossible, adaptation is impossible, the percentage overall is way not large enough and so on. Sadly, people still stick to this as a primary approach, giving the public a good feeling about this ("oh we destroyed that landscape, but we set up part of it as a nature reserve") which eliminates the need for them to think larger...