Over the past 200 years, thousands of foreign plant and animal species have become established in the United States. About one in seven has become invasive. The invasive species typically have high reproductive rates, disperse easily, and can tolerate a wide range of environmental conditions. Often, they lack predators in their new environments. As a result, invasives may outcompete native flora and fauna for biological niches carved out over millennia.
Some non-native species, intentionally introduced for beneficial purposes, later turn out to be invasive. Examples include saltcedar, which was introduced for erosion control, or the feral pigs here at Pinnacles National park. 138 billion dollars is the price-tag put by Cornell University researchers on the invasive species-induced costs of ecosystem damages, reduced crop yields, control efforts and lost forest products in the United States alone. The ecological costs of invasive species are also staggering. They eat, outcompete, and hybridize with native species, spread diseases, and eliminate or change native habitats. In the United States, 400 of the 958 species listed as threatened or endangered under the Endangered Species Act are at risk primarily because of competition with and predation by non-indigenous species. In some areas of the world, this proportion is much higher. In fact, the impact of invasive species is second only to direct habitat destruction, such as clearcutting, among the causes of extinction. The undoing is not limited to habitats and non-humans; we are also losing people, languages and cultures. The land of Pinnacles National park began to be protected in the early 1900's. That does not mean that the land is unaltered, but that it has been buffered from invasive species. The park's harsh climate, with large daily temperature fluctuations and hot, dry summers also buffers Pinnacles from invasives, because fewer invasives are able to thrive here. Pinnacles National park is special today in part due to its relatively high proportion of native plants and animals, and comparatively undisturbed land. We seek to preserve the health of the park's habitats by controlling exotic plants and feral pigs, as detailed in the highlights above.