The northern region uplands are dominated by pine, originally longleaf and slash in the south and shortleaf mixed with hardwoods in the north. These are wildfire-maintained systems that give way to loblolly pine and hardwoods in damper areas and bottomland hardwood forest in extensive lowland drainages. The southern region has tropical and subtropical moist broadleaf forests and western Gulf coastal grasslands. They include large habitats of freshwater wetlands, salt marshes, and coastal mangrove swamps. Much of the lower elevation Gulf Coastal Plain supports wintering waterfowl. Groundwater A global satellite study by German and USA scientists spanning the last decade indicates groundwater resources are shrinking due to overuse causing regional water security uncertainty in a changing climate. Surface water quality is declining due to increasing population, depleted streams, and land subsidence along certain coastlines. The Atlantic and Gulf Coastal Plain Aquifer is considered to have low to moderate stress, but the region's economic capacity and land-use patterns signal trends toward a human-dominated stress on water resources. References External links USDA - Center for Bottomlands Hardwood Research website Gulf Coastal Plain Ecosystem Partnership (GCPEP) website Landforms of the Gulf of Mexico Plains of the United States Regions of the Southern United States Regions of Texas Plains of Mexico Landforms of Tamaulipas Landforms of Veracruz Landforms of Florida Landforms of Mississippi Landforms of Missouri Landforms of Tennessee Landforms of Kentucky Landforms of Arkansas Landforms of Louisiana Landforms of Oklahoma Landforms of Texas Physiographic sections Physiographic regions of Mexico Physiographic regions of the United States