Habitat change has greater effects than climate change on butterfly occurrence in South Korea

We examined the influence of climate and habitat changes on the occurrence of butterflies in South Korea, using data recorded in two different periods: (i) past (1938–1950) and (ii) present (1996–2011). Butterfly species were classified according to their distribution types (northern, southern, and miscellaneous) to examine the effect of climate change. They were also classified according to three different habitat types (forest interior, forest edge, and grassland) to examine the effect of habitat change. Three types of food niche (monophagous, oligophagous, and polyphagous) were identified. A community temperature index (CTI), based on the species temperature index of each species, was calculated for past and present butterfly communities to estimate range shifts of butterflies at the community level. At the species level, range shifts of butterflies were calculated as a shift of the mid-zone of the distribution range in terms of latitude and temperature. The results showed that a change in the occurrence of butterflies was not significantly different among the three distribution types. The CTIs were not different between past and present communities, and the mid-zones of distribution range in latitude and temperature did not change. These results indicate that the occurrence change of butterflies was not significantly influenced by climate change but was instead influenced by habitat change from bare-ground or grassland to forests over 60 years. There was an increase in forest species and a decrease in grassland species, reflecting the effects of large-scale reforestation in South Korea over the last few decades. The reforestation has resulted in an increase in monophagous (oak-feeding) butterflies. Our results show that habitat change played a key role in the occurrence of Korean butterflies and may be confounding any possible influence of climate change.