Generate Key TakeawaysThe National Park Service says invasive species are posing challenges to natural ecosystems, leading to threats to native wildlife and even humans. Rangers say some of the invasive pests have been introduced accidentally, while others have been intentionally released into the wild. Why Buying Local Firewood Can Limit The Spread Of Invasive SpeciesThe NPS considers free-ranging cats to be among the widespread invasive problems throughout more than 400 sites. Three other types of invasive pests that park staff identified are rather small and sometimes require a magnifying glass to properly see. Original article source: Cats among top 5 invasive pests in America’s national parks