What habitats are worth saving?

The Serengeti World Heritage site is in grave danger as the Tanzanian Government moves forward with highway construction. Even though statements have been made that a road to the south would not help transportation problems of those North of the park and that it would severly damage the ecosystems, plans still remained for construction. The northern parts of the Serengeti are in fact the only year-round water source for wildabeest and zebras.
In the northern part of the globe polar bears are facing mass destruction. Their habitats are being destroyed because pollutants are being dumped into the water, polar ice is fastly dissappearing because of climate change, and oil and natural gas have been discovered. Scientists expect the decline of polar bears to continue and by 2050 the population will be about 70 percent less than it is today, facing high extinction.
Orangutans, "the person of the forest," which once thrived in Southeast Asia are dying at an alarming rate. Their forest homes have disappeared 80 percent in the last twenty yearts. The logging industry is literally killing orangutans and many other species that live in the trees.
Animals are certainly the first thing many people think about saving in an environmental setting, but what about the plants? When constructing highways and buildings we use miles of precious land. When we tear down forests we are destroying thousands of plant species and making the world less healthy for all animals and humans.