Mechanistic studies have documented extinctions due to recent climate change: McLaughlin et al. documented two populations of Bay checkerspot butterfly being threatened by precipitation change.[16] Parmesan states, "Few studies have been conducted at a scale that encompasses an entire species"[17] and McLaughlin et al. agreed "few mechanistic studies have linked extinctions to recent climate change."[16] Daniel Botkin and other authors in one study believe that projected rates of extinction are overestimated.[18] For "recent" extinctions, see Holocene extinction.