When Karla Colom zips down the Paseo del Morro National Historical Trail at sunset in a golf cart loaded with food, water and cleaning supplies, the cats of Old San Juan come out of hiding. Colony by colony, they materialize from nooks in the rocks along the ocean and hiding places in the greenery at the foot of ancient walls built to protect the Puerto Rican city from attack by sea.

From the loss of the passenger pigeon, perhaps the most lamented extinction case in the United States, to the writing off of the Kaua’i nukupu’u, a Hawaiian forest bird vanished for more than a century and just recently officially declared extinct, the disappearance of species whittles away at the country's biodiversity and attachment to nature.

A draft plan crafted to see grizzly bears restored to the North Cascades Ecosystem of Washington state proposes to release bears that would be treated as a "nonessential experimental population," a designation that would provide more options for managing the species, which currently is protected under the Endangered Species Act. The last confirmed sighting of a grizzly bear in the U.S. portion of the ecosystem was in 1996.

A few areas of Big Bend National Park in Texas will be closed beginning October 3 to allow for removal of non-native aoudad sheep.