billion on their sport. In the US, proceeds from hunting licences contribute to state game management programs, including preservation of wildlife habitat. Hunting contributes to a portion of caloric intake of people and may have positive impacts on greenhouse gas emissions by avoidance of utilization of meat raised under industrial methods. Environmental problems Lead bullets that miss their target or remain in an unretrieved carcass could become a toxicant in the environment but lead in ammunition because of its metallic form has a lower solubility and higher resistance to corrosion than other forms of lead making it hardly available to biological systems. Waterfowl or other birds may ingest the lead and poison themselves with the neurotoxicant, but studies have demonstrated that effects of lead in ammunition are negligible on animal population size and growth. Since 1991, US federal law forbids lead shot in waterfowl hunts, and 30 states have some type of restriction. In December 2014, a federal appeals court denied a lawsuit by environmental groups that the EPA must use the Toxic Substances Control Act to regulate lead in shells and cartridges. The groups sought EPA to regulate "spent lead", yet the court found EPA could not regulate spent lead without also regulating cartridges and shells. Conservation Hunters have been driving forces throughout history in the movement to ensure the preservation of wildlife habitats and wildlife for further hunting. However, excessive hunting and poachers have also contributed heavily to the endangerment, extirpation and extinction of many animals, such as the quagga, the great auk, Steller's sea cow, the thylacine, the bluebuck, the Arabian oryx, the Caspian and Javan tigers, the markhor, the Sumatran rhinoceros, the bison, the North American cougar, the Altai argali sheep, the Asian elephant and many more, primarily for commercial sale or sport. All these animals have been hunted to endangerment or extinction. Poaching currently threatens bird and mammalian populations around the world. The 2019 Global Assessment Report on Biodiversity and Ecosystem Services lists the direct exploitation of organisms, including hunting, as the second leading cause of biodiversity loss, after land use for agriculture. In 2022, IPBES released another report which stated that unsustainable hunting, along with unsustainable logging and fishing, are primary drivers of the global extinction crisis. Legislation Pittman–Robertson Wildlife Restoration Act of 1937 In 1937, American hunters successfully lobbied the US Congress to pass the Pittman-Robertson Wildlife Restoration Act, which placed an eleven