Top States for Biodiversity

Chaparral, a very diverse plant community in coastal California.
David McNew/Getty Image News

Biodiversity is the richness of life in all of its forms, from genes to ecosystems. Biodiversity is not distributed equally over the globe; several factors combine to create so-called hotspots. For example, the Tropical Andes in South America has many more species of plants, mammals, or birds than almost anywhere else on the planet. Here, let’s examine the number of species in individual states, and see where North America’s hotspots are located. The rankings are based on the distribution of 21,395 plant and animal species represented in the databases of NatureServe, a non-profit group devoted to supplying information on the status and distribution of biodiversity.

The Rankings

  1. California. The richness of California’s flora makes it a biodiversity hotspot even in global comparisons. A lot of that diversity is driven by the large variety of landscapes found in California, including the driest of deserts, lush coastal coniferous forests, salt marshes, and alpine tundra. Mostly separated from the rest of the continent by high elevation mountain ranges, the state has a large number of endemic species. The Channel Islands off California’s southern coast provided even more opportunities for the evolution of unique species.
  2. Texas. Like in California, the species richness in Texas comes from the state's sheer size and the variety of ecosystems present. In a single state, one can encounter ecological elements from the Great Plains, the southwestern deserts, the rainy Gulf Coast, and the Mexican subtropics along the Rio Grande. In the heart of the state, the Edwards Plateau (and its numerous limestone caves) holds a rich diversity and many unique plants and animals. The Golden-cheeked Warbler is a Texas endemic relying on the juniper-oak woodlands of the Edwards Plateau.
  3. Arizona. At the junction of several great arid ecoregions, Arizona’s species richness is dominated by desert-adapted plants and animals. The Sonoran Desert in the southwest, the Mojave Desert in the northwest, and the Colorado Plateau in the northeast each bring a unique suite of arid land species. The high elevation woodlands in the mountain ranges add to this biodiversity, especially in the southeast portion of the state. There, small mountain ranges collectively referred to as the Madrean Archipelago carry pine-oak forests more typical of the Mexican Sierra Madre, and along with them species reaching the very northern end of their distribution.
  4. New Mexico. This state’s rich biodiversity also comes from being at the intersection of several major ecoregions, each with unique plants and animals. For New Mexico, much of the biodiversity comes from the Great Plains influences in the east, the Rocky Mountains incursion in the north, and the botanically diverse Chihuahuan Desert in the south. There are small but significant inclusions of the Madrean Archipelago in the southwest and the Colorado Plateau in the northwest.
  5. Alabama. The most diverse state east of the Mississippi, Alabama benefits from a warm climate, and the absence of recent biodiversity-leveling glaciations. Much of the species richness is driven by the thousands of miles of freshwater streams running through this rain-soaked state. As a result, there is an unusually high number of freshwater fish, snails, crayfish, mussels, turtles, and amphibians. Alabama also boasts a variety of geological substrates, which support different ecosystems in sand dunes, bogs, tallgrass prairies, and glades where the bedrock is exposed. Another geological manifestation, extensive limestone cave systems, supports many unique animal species.


NatureServe. States of the Union: Ranking America’s Biodiversity.