One individual CAN make a difference, and even small efforts can add up to big change when people work together. In the 1970s Americans recycled only about seven percent of their trash. Today we recycle almost 34 percent, and our landfill use has decreased by about 30 percent. While we still have a way to go, a lot of individuals recycling their soda cans and newspapers have added up to a big difference.
Our actions can lead to change for the better or irreparable loss. In 1922 a national monument was created in South Dakota to preserve a large concentration of fossils. Unfortunately you will never be able to visit Fossil Cycad National Monument. By 1957 virtually all the fossils were gone, and the monument was decommissioned. Many were probably taken as souvenirs by people who thought that taking "just one" wouldn't make a difference.
On the other hand, many of our national parks would not be here today if it weren't for individuals working together. Without Marjory Stoneman Douglas and other concerned citizens, the Everglades would have been drained for development. Giant sequoia trees would have been cut down to make toothpicks, if not for the lobbying efforts by John Muir and other conservationists. Thanks to their efforts, Everglades and Sequoia national parks are protected for future generations.
Many small actions led to the climate change we see now; it will take many small actions to reverse it. As Margaret Mead famously said, "Never doubt that a small group of thoughtful committed citizens can change the world; indeed, it's the only thing that ever has."