Quantifying Methane Emissions from Aquaculture Ponds in China.

Small ponds are important methane (CH4) sources. However, current estimates of CH4 emissions from aquaculture ponds are largely uncertain due to data paucity, especially in China─the largest aquaculture producer in the world. Here, we present a nationwide metadata analysis with a database of 55 field observations to examine total CH4 emissions from aquaculture ponds in China. We found that the annual CH4 fluxes from aquaculture ponds are much larger than those from reservoirs and lakes. The total CH4 emission from aquaculture ponds is 1.60 ± 0.62 Tg CH4 yr-1, with an average growth rate of ∼0.03 Tg CH4 yr-2 during the period 2008-2019. Compared with global major protein-producing livestocks, aquaculture species have a lower (63%) emission intensity, defined by the amount of CH4 emitted per unit of animal proteins. Our study highlights the essential contribution of China's aquaculture ponds to national CH4 emissions and the lower environmental cost of the aquaculture sector for future animal protein production. More field measurements with multi-scale observations are urgently needed to reduce the uncertainty of CH4 emissions from aquaculture ponds.

Non-growing season drought legacy effects on vegetation growth in southwestern China.

Water availability influences terrestrial ecosystems' composition, structure, and function. Recently, climate change increased drought periods frequency and length in many parts of the world, including southwestern China, a biodiversity hotspot. Although the drought impacts on ecosystems are well known, studies are scarce in subtropical areas of China. This work studied the drought legacy effects on vegetation growth in southwestern China using Normalized Difference Vegetation Index (NDVI) and the Standardized Precipitation Evapotranspiration Index (SPEI), with a particular focus on non-growing season extreme drought events. Pervasive non-growing season drought legacy effects were found in the first growing season in most parts of southwestern China. The highest impacts were identified in forests, while the effects in grass were less severe. At the regional scale, horizontal and vertical spatial patterns of drought legacy effects were heterogeneous, and the highest impacts were found in warmer and wetter forests and alpine grasslands. Our study highlights that severe drought conditions may dramatically affect vegetation growth in southwestern China.