The conservation body of the United Nations has offered wider, stronger protection to 31 species of animals, including a variety of vulnerable birds, sharks and whales.

The species were granted new, more protective classification only after several days of intense debate among conservationists from across the globe.

At the closing of the Convention on Migratory Species conference in Ecuador, not all 31 species received the same level of protection. Some species were upgraded to an Appendix II listing, which requires international cooperation in organizing comprehensive conservation plans. Other, more vulnerable species were granted an Appendix I listing -- the strongest level of protection, including bans on killing and other similarly strict measures.

The most iconic species to be re-listed was the polar bear, which remains increasingly threatened by melting ice, Arctic oil exploration and hunting. The polar bear is now included in Appendix II.

"We are pleased to see the polar bear joining a growing list of threatened migratory species protected under CMS," Masha Vorontsova, director of the International Fund for Animal Welfare Russia, told The Guardian. "Appendix II does not mean that sufficient conservation action will be taken to protect the well-being of polar bears."

"What gives us hope is that this listing means that 120 countries are now recognizing the threats that polar bears face from the shrinking of their ice habitat to pollution and hunting," Vorontsova added. "This is an important first step, but it must not be the last if we wish to save the polar bear."

Perhaps the biggest winners in Ecuador were sharks -- 21 species of sharks, rays and sawfish were added to the UN's list of protected species. Sharks and whales can be particularly hard to protect as they migrate across large swaths of ocean, across international boundaries. New listings and agreements forged at the 120-nation conference will attempt to address such issues.

"That means where the species migrates, that all of those countries come up with a strategy, a strategic plan to be able to manage and conserve those species," Bradnee Chambers, the convention's executive secretary, told Bloomberg.

"For species like silky and thresher sharks, there's still time to save them, but the time for action is now," said Luke Warwick, a conservation advocate with Pew Charitable Trusts' shark conservation initiative. "The implementation of these listings will be key."

Other species that also saw their protection level strengthened are the extremely rare Cuvier's beaked-whale, Africa's red-fronted gazelle, and the great bustard, a bird found in Europe and Asia.