In some species, gender is determined by genetics, one pair of chromosomes will produce a male, another pair a female. However, in other species, mostly the reptile or amphibian families, gender is dependent on the temperature in which the eggs are hatched. Called the thermosensitive period of gestation it can last for 7-15 days and once passed, the gender that develops does not change. Eastern bearded dragons, komodo dragons and some alligators lay eggs that are temperature dependent. Temperature in the environment is not a constant though, and variations can affect the population of certain species.
The problem is that in some areas, climate change, specifically the warming of waters and other habitats is causing the ratios of females to males to change. It gets even more complicated, because depending on the species, warmer temps can mean a male offspring will develop, but in others it means a female. Either way, the increasing temperatures that have come about as a result of climate change are impacting the numbers of females and males. When this ratio is disrupted, as it seems to be happening recently as a result of global warming, it could mean a decline in the species if there are not enough males to breed with an increase in females or vice versa.