areas. And finally, regular cycles of mowing and cutting, as well as the use of herbicides can both inhibit and benefit various wildflowers and plant species growing there. Most plant species at any given roadside represent the association immediately adjacent to that locality, but often have a few odd of species from other areas. Roadsides are a convenient and accessible places to view wildflowers, regardless of whether they are true ecosystems. In the past some (including the National Park Service) have discussed the river edge as an ecosystem in the Big Thicket however, most ecologist do not recognize river edges as an ecosystem distinct from the one a river runs through. Exact numbers of plant and animal species occurring in the Big Thicket region are difficult to state objectively due to a number of factors including: the imprecise boundaries of the area; which (if any) accidental and vagrant species to count; whether to count extinct and extirpated species; whether to count introduced and invasive species; migratory vs. resident species; frequent taxonomic changes and taxonomic instability. These and other factors all contribute to what sometimes appear as inconsistent or contradictory counts and numbers. Flora The area contains over 100 species of trees and shrubs, with longleaf pine (Pinus palustris) once dominating the region. Big Thicket National Preserve has introduced programs to re-establish this dominance, including one of the US's most active prescribed burn programs. With the National Park Service's centennial occurring in 2016, efforts were made to plant between 100,000 and 300,000 longleaf pines. The National Park Service lists more than one thousand species of flowering plants and ferns that can also be found in the thicket, including 20 orchids and four types of carnivorous plants. Fauna During the last glacial period, plant and animal species from many different biomes moved into the area. Before their extinction, the Big Thicket was home to most species of North American megafauna. Well over 500 species of vertebrates occur in the Big Thicket region, including more than 50 mammals, 300 birds, 60 reptiles, 30 amphibians, and over 90 fishes. The records and numbers below for mammals, reptiles, and amphibians are based on county records for Hardin, Jasper, Liberty, Montgomery, Polk, San Jacinto, Tyler, and Walker counties, which in a few cases may reflect marginal, peripheral, and vagrant records for a given species in the region and not all of the species are ubiquitous or