There are many nature and conservation organizations wanting our money. Many of them do very little real work and are actually in the business of whining about global warming or else being against everything and anything. There are, however, at least two organizations that do great work and earn every donation they get.
The first of these is the Student Conservation Association (SCA). In their own words, "SCA provides college and high school-aged members with hands-on conservation service opportunities in virtually every field imaginable, from tracking grizzlies through the Tetons to restoring desert ecosystems and teaching environmental education at Washington, D.C.’s Urban Tree House. We are truly building the next generation of conservation leaders." What this means in a practical sense is that SCA members do real work at National Parks and similar areas. The parks truly would not function as well without them. They supplement the staff, save our tax dollars, and learn something useful at the same time. One of my favorite pastimes at National Parks is chatting with rangers. Many of them say that they were in the SCA. Enough said. Get out your checkbook.
The second organization is the National Parks Conservation Association (NPCA). They do political rather than physical labor, but that is no less important. Their mission is "to protect and enhance America's National Parks for present and future generations." More specifically:
"We advocate for the national parks and the National Park Service; we educate decision makers and the public about the importance of preserving the parks; we help to convince members of Congress to uphold the laws that protect the parks and to support new legislation to address threats to the parks; we fight attempts to weaken these laws in the courts; and we assess the health of the parks and park management to better inform our advocacy work." I have been donating to them for years. As an extra bonus, they have a great magazine, National Parks.