National parks are important for preserving biodiversity by supporting ecosystems and the flora that live within them, for protecting the environment by providing sustainable energy and mitigating the effects of climate change, and for national and local economies by promoting tourism and protecting agriculture. The value of these benefits exceeds $13 billion per year. In addition to their environmental benefits, national parks provide opportunities for visitors to have an impact by helping with conservation efforts or simply by enjoying the beauty of the park. For example, visitors can help conserve wildlife by staying on designated trails and not feeding the animals, which can lead them to become habituated to humans and make them more vulnerable to being killed by vehicles. They can also help protect habitats by avoiding littering and cleaning up after themselves, removing invasive species, and planting native plants. National parks also benefit local communities by providing jobs in tourism and recreation, as well as commerce related to those activities. On average, there are between 20,000 and 26,000 jobs associated with national parks and protected areas. These jobs represent about 2% of all national park-related employment. National parks serve as landmarks and help define a nation's character. They also provide essential habitat for many species, allow people to experience unique natural features, and give Americans a reason to celebrate our country every year at National Park Week.