User:Advythr/Pleistocene megafauna

Community and ecosystem changes
Megafauna extinctions resulted in global changes to ecosystem structure and function. Extinction of megafauna broadly restructured ecological communities, reducing the strength of biotic drivers. Some evidence, however, suggests that vegetation changes preceded megafaunal extinctions. Evidence from fossil pollen indicates that megafaunal extinctions may have resulted in the development of novel plant communities, and altered fire regimes on a global scale. Some hypothesize that forbs in modern grasslands are adapted to disturbance by large herbivores on former mammoth steppes, and are currently in decline due to the extinction of Pleistocene megafauna. In Europe, evidence from the pollen record suggests that megafauna promoted open vegetation with shifting mosaics of forest and grassland, however this hypothesis is debated. In the Yukon region of Canada, the decline of Mammuthus and Equus may have contributed to the development of woody flora. The extinction of megafauna also affected mutualist species, resulting in co-extinctions. Some argue that modern ecosystems can be understood by considering the effects of extinct megafauna.

Anachronistic plants
Some extant plants have adaptations resulting from interactions with Pleistocene megafauna, including defenses against Pleistocene megaherbivores, and large fruits adapted to dispersal by megaherbivores. Such species are termed anachronistic plants. Megafaunal extinction caused the decline of Cucurbita species which relied on megaherbivores for dispersal. Some argue that plant adaptations to megafauna resulted in traits that allowed for domestication.

Effects on climate
Megafaunal extinction may also resulted in global cooling of the Earth's climate due to reduced methane emissions from megaherbivores and increased woody vegetation associated with reduced trampling and browsing. Smith et al. suggest that megafaunal extinctions in the Americas contributed to the Younger Dryas cooling event.

Younger Dryas impact hypothesis
Some scientists argue that an extraterrestrial impact contributed to megafaunal extinctions.