Effect of climate-change-induced increases on the range of rice-barley double cultivation on the intermediate egret

Intensification of cultivation methods and land use types, particularly in
the face of climate change, has steadily weakened the habitat function of
rice fields for waterbirds. Intermediate egrets (Ardea intermedia) are
highly dependent on rice field habitats. Here, we examine the effect of a
shift from rice monoculture to rice–barley double cultivation on the use
of rice fields by intermediate egrets in South Korea. Rice-barley double
cultivation has been increasing steadily in the southern region of South
Korea due to changes in the rice growth period under climate change and
maximization of economic benefits. We studied rice fields to determine the
effect of the rice-barely double cultivation area on the abundance of
intermediate egrets on the regional scale and their potential distribution
pattern in response to double cultivation in relation to climate change
using national-scale climate, altitude, and land cover data from May 1 to
June 23, 2018. Compared to the irrigation practices used for rice
monoculture, irrigation was stopped for some time in rice-barley double
cultivation prior to planting, compromising the role of rice fields as a
food ground for intermediate egrets. The potential abundance of
intermediate egrets rapidly decreased by half when the double cultivation
area increased to >40% of the total rice-field area, and was less
than one individual if the area increased to >80%. Furthermore,
according to climate change projections, by 2100, the double cultivation
area would account for 75.74% of the predicted range of intermediate egret
foraging ground. Synthesis and applications. Double cultivation areas
should be <40% of existing rice fields to minimize the impact of
the change in cultivation practices. This approach can also convert rice
fields to other types of land use. Consequently, appropriate conservation
and management measures may be developed to maintain suitable habitats
despite rapidly changing cultivation practices resulting from climate
change.