Plants become rare and endangered due to natural or human causes or a combination of the two, according to Celebrating Wildflowers, a U.S. Forest Service website. Natural causes are often unknown. Habitat lost to development, plant collecting in the wild and introduction of invasive plants are human causes of plant depletion. "Endangered" means a plant is close to being extinct, and is a legal term defined by the federal government as part of the Endangered Species Act.
History of the Endangered Species Act
The Federal Endangered Species Act (ESA) was enacted in 1973 to provide protection to plants and animals in danger of extinction. This act expanded on a previous piece of legislation enacted in 1966 that involved animals only and gave limited protections. Once a plant is listed as endangered, the government is able to take action, such as purchasing land within the plant's habitat. According to the U.S. Forest Service, 764 plants are currently protected under the ESA.
The U.S. Forest Service has determined that 8,440 plants are rare; a number that is approximately one-third of all native plants. Rare plants that are not protected under the Endangered Species Act will still have assistance by the U.S. Forest Service through such measures as habitat protection and curbing the spread of non-native invasive plants. Individual states also have lists of plants that are rare, threatened and endangered and measures in place to protect them.
In addition to habitat loss and encroachment of invasive species, rare plants face other challenges. The University of British Columbia Botanic Garden and Centre for Plant Research cites rising nitrogen levels from pollution and fertilizers as one reason rare plants are in jeopardy. Taller plants in an ecosystem thrive in the extra nitrogen, fatally shading the smaller plants. Plants are also affected by such natural challenges as not having pollinators or growing in too specialized a habitat.
State Laws for Endangered Plants
According to the U.S. Forest Service, 32 states have laws protecting endangered plants. State-level protection is usually not as strong as that of the Endangered Species Act. As is the case with the ESA, most states don't have the jurisdiction to protect plants on private lands. Under the ESA, animals are protected on private lands, a difference that harkens back to English common law where the king owned all the animals, but the plants on the land belonged to the landowner.
State and federal governments purchase land where endangered plants are growing and put programs in place, such as controlled burns to keep prairie habitats open. The Center for Plant Conservation stores material from 700 "imperiled" plant species in seed banks in case of their extinction in the wild. In a 2009 article in The New York Times, Anne Raver reports on a controversial seed-banking plan called "assisted migration" should climate change so alter conditions that plants need to be moved to survive.
According to the U.S. Forest Service, almost all of the world's population of Robbins' cinquefoil (Potentilla robbinsiana) occurred on one acre of trail in New Hampshire's White Mountains. Plant collecting and hiking over 150 years had almost made this cinquefoil extinct. The trail was relocated in 1983 and in the 1990s, the New England Wildflower Society began work to propagate new plants. In 2002, Robbins' cinquefoil was taken off the endangered list. As of 2006, numbers were up from 1,801 plants to 4,883.