1. State Key Laboratory of Nutrient Use and Management, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China 2. College of Resources and Environmental Sciences, Yunnan Agricultural University, Kunming 650201, China 3. Guangdong-Hong Kong Joint Laboratory for Water Security, Center for Water Research, Advanced Institute of Natural Sciences, Beijing Normal University, Zhuhai 519087, China 4. Lishui Institute of Ecological Environment, Nanjing University, Nanjing 211200, China 5. Key Laboratory of Agro-Environment in downstream of Yangze Plain, Ministry of Agriculture and Rural Affairs of China, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China 6. College of Resources and Environmental Sciences, Hebei Agricultural University, Baoding 071001, China 7. Wageningen Environmental Research, Wageningen University and Research, 6700 AA Wageningen, the Netherlands
● Erhai Lake basin faces the duel challenge of enhancing water protection and increasing farmer income.
● A new framework indicates the key strategies for tackling the multiple challenges of agricultural green development in Erhai.
● The needs for interdisciplinary research innovation and smallholder enabled technology transformation identified.
● Building trust and partnerships between farmers, citizens, local government, industry and extension services should be prioritized.
● Agricultural green development in Erhai can serve as a model for other high-altitude lake basins.
Pollution of high-altitude lake basins by agriculture and rural activities, and the control of this pollution, have received increasing attention from academic research and government policy in China. Series of restrictions and regulations have been implemented to protect the surface water quality. These restrictions and regulations have greatly impacted and transformed the agricultural systems and rural livelihoods surrounding these lake basins. Using Erhai Lake basin in Yunnan Province as a case study, three main challenges were identified for concurrently decreasing pollution in the lake and increasing farmer income. It is contended that scientifically-sound environmental protection policies and agricultural green development practices are key to reversing the current situation. This will help to protect the lake from pollution while smallholder farmers will be able to produce healthy food in an environmentally sustainable manner, and with a fair remuneration for all the services farmers provide to the society.
Box 1 Erhai Lake and catchment Erhai is a tectonic lake (developed in a geological fault) in Dali, Yunnan (25°45′48″ N, 100°11′15″ E) at 1972 masl. It has a length of about 40 km, a width of 7 km, and a surface area of 250 km2. Mean water depth is about 11 m. It is the seventh largest freshwater lake in China. The catchment area is about 2250 km2 (Fig.1). The lake drains out through the Xier River to the south which eventually joining the Mekong River. The lake had high biodiversity and has been a main food source for the local Bai people. However, fishing (plus boating and swimming) has been forbidden by the government since 2015, because of declining water quality and biodiversity. The lake is surrounded by mountains that reach heights of more than 4000 masl with forests above 3000 masl. The slightly sloping floodplains on the western and northern shores are intensively cropped and also rather densely populated. The main crops are paddy rice, tobacco, maize, vegetables and beans grown in double cropping systems (2 crops per year). Most crops are irrigated, with water intercepted from the surrounding mountains and taken from Erhai Lake. There are four towns and 52 villages in the catchment, with a total population of nearly 1 million, but most people live on the floodplains of the western shore. The lake and its surroundings are attracting millions of visitors each year. Both, the intensive agricultural practices, households and tourists put pressure on the lake. From 2015, the governments have implemented several initiatives to protect the lake from further pollution.
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1
J, Huisman G A, Codd H W, Paerl B W, Ibelings J M H, Verspagen P M Visser . Cyanobacterial blooms. Nature Reviews: Microbiology, 2018, 16(8): 471–483 https://doi.org/10.1038/s41579-018-0040-1
2
J, Zhou P R, Leavitt Y, Zhang B Qin . Anthropogenic eutrophication of shallow lakes: Is it occasional. Water Research, 2022, 221: 118728 https://doi.org/10.1016/j.watres.2022.118728
3
of Ecology and Environment of the People’s Republic of China (MEEPRC) Ministry . China’s Ecological and Environmental Situation Bulletin 2022. MEEPRC, 2023 (in Chinese)
4
X, Liu X, Wang K, Chen D Li . Simulation and prediction of multi-scenario evolution of ecological space based on flus model: a case study of the Yangtze River Economic Belt, China. Journal of Geographical Sciences, 2023, 33(2): 373–391 https://doi.org/10.1007/s11442-023-2087-9
5
Z, Pan G, Gao B Fu . Spatiotemporal changes and driving forces of ecosystem vulnerability in the Yangtze River basin, China: quantification using habitat-structure-function framework. Science of the Total Environment, 2022, 835: 155494 https://doi.org/10.1016/j.scitotenv.2022.155494
6
X, Xu G, Yang Y, Tan J, Liu H Hu . Ecosystem services trade-offs and determinants in China’s Yangtze River Economic Belt from 2000 to 2015. Science of the Total Environment, 2018, 634: 1601–1614 https://doi.org/10.1016/j.scitotenv.2018.04.046
7
G, Ma J, Xiao Q, Li L, Zhang B, An G, Sun H, Cheng J, Tang H Li . Impact of the evolution of Plateau Lake landscape pattern on ecosystem service value in the Pearl River basin: a case study of Yilong Lake Basin in Yunnan Province, China. Acta Geophysica, 2023, 71(3): 1391–1407 https://doi.org/10.1007/s11600-022-00777-9
8
X, Dai Y, Zhou W, Ma L Zhou . Influence of spatial variation in land-use patterns and topography on water quality of the rivers inflowing to Fuxian Lake, a large deep lake in the plateau of southwestern China. Ecological Engineering, 2017, 99: 417–428 https://doi.org/10.1016/j.ecoleng.2016.11.011
9
S, Tao J, Fang S, Ma Q, Cai X, Xiong D, Tian X, Zhao L, Fang H, Zhang J, Zhu S Zhao . Changes in China’s lakes: climate and human impacts. National Science Review, 2020, 7(1): 132–140 https://doi.org/10.1093/nsr/nwz103
10
X, Chen X, Liu B, Li W, Peng F, Dong A, Huang W, Wang F Cao . Water quality assessment and spatial-temporal variation analysis in Erhai Lake, Southwest China. Open Geosciences, 2021, 13(1): 1643–1655 https://doi.org/10.1515/geo-2020-0326
11
Z, Ni S Wang . Historical accumulation and environmental risk of nitrogen and phosphorus in sediments of Erhai Lake, Southwest China. Ecological Engineering, 2015, 79: 42–53 https://doi.org/10.1016/j.ecoleng.2015.03.005
12
S, Wang L, Zhang L, Ni H, Zha L, Jiao S, Yang L, Guo J Shen . Ecological degeneration of the Erhai Lake and prevention measures. Environmental Earth Sciences, 2015, 74(5): 3839–3847 https://doi.org/10.1007/s12665-015-4433-4
13
S, Lin S L, Shen A, Zhou H M Lyu . Sustainable development and environmental restoration in Lake Erhai, China. Journal of Cleaner Production, 2020, 258: 120758 https://doi.org/10.1016/j.jclepro.2020.120758
14
Q Wang . Mid-term assessment report of the 13th Five-Year Plan for the protection of ecological environment. In: Wang J, Wang X, Wan J, eds. Environmental Strategy and Planning in China. Springer, 2022, 205–224
15
S S, Lin S L, Shen A, Zhou H M Lyu . Assessment and management of lake eutrophication: a case study in Lake Erhai, China. Science of the Total Environment, 2021, 751: 141618 https://doi.org/10.1016/j.scitotenv.2020.141618
16
Z, Cui H, Zhang X, Chen C, Zhang W, Ma C, Huang W, Zhang G, Mi Y, Miao X, Li Q, Gao J, Yang Z, Wang Y, Ye S, Guo J, Lu J, Huang S, Lv Y, Sun Y, Liu X, Peng J, Ren S, Li X, Deng X, Shi Q, Zhang Z, Yang L, Tang C, Wei L, Jia J, Zhang M, He Y, Tong Q, Tang X, Zhong Z, Liu N, Cao C, Kou H, Ying Y, Yin X, Jiao Q, Zhang M, Fan R, Jiang F, Zhang Z Dou . Pursuing sustainable productivity with millions of smallholder farmers. Nature, 2018, 555(7696): 363–366 https://doi.org/10.1038/nature25785
17
W, Zhang G, Cao X, Li H, Zhang C, Wang Q, Liu X, Chen Z, Cui J, Shen R, Jiang G, Mi Y, Miao F, Zhang Z Dou . Closing yield gaps in China by empowering smallholder farmers. Nature, 2016, 537(7622): 671–674 https://doi.org/10.1038/nature19368
18
Y, Wu J, Zhang Z, Hou Z, Tian Z, Chu S Wang . Seasonal dynamics of algal net primary production in response to phosphorus input in a mesotrophic subtropical plateau lake, southwestern China. Water, 2022, 14(5): 835 https://doi.org/10.3390/w14050835
19
Z, Wen X, Li B, Liu T Li . A comprehensive evaluation method for plateau freshwater lakes: a case in the Erhai Lake. Ecosystem Health and Sustainability, 2021, 7(1): 1993753 https://doi.org/10.1080/20964129.2021.1993753
20
A, Xu L E, Yang W, Yang H Chen . Water conservancy projects enhanced local resilience to floods and droughts over the past 300 years at the Erhai Lake basin, Southwest China. Environmental Research Letters, 2020, 15(12): 125009 https://doi.org/10.1088/1748-9326/abc588
21
K, Gelsey H, Chang D Ramirez . Effects of landscape characteristics, anthropogenic factors, and seasonality on water quality in Portland, Oregon. Environmental Monitoring and Assessment, 2023, 195(1): 219 https://doi.org/10.1007/s10661-022-10821-2
22
Y, Dong Y, Guo Y, Wang W Zeng . Spatial and temporal evolution of the “source-sink” risk pattern of NPS pollution in the upper reaches of Erhai Lake basin under land use changes in 2005–2020. Water, Air, and Soil Pollution, 2022, 233(6): 202 https://doi.org/10.1007/s11270-022-05662-1
23
E D, Ongley Z, Xiaolan Y Tao . Current status of agricultural and rural non-point source pollution assessment in China. Environmental Pollution, 2010, 158(5): 1159–1168 https://doi.org/10.1016/j.envpol.2009.10.047
24
T, Zhang A, Chen J, Liu H, Liu B, Lei L, Zhai D, Zhang H Wang . Cropping systems affect paddy soil organic carbon and total nitrogen stocks (in rice-garlic and rice-fava systems) in temperate region of southern China. Science of the Total Environment, 2017, 609: 1640–1649 https://doi.org/10.1016/j.scitotenv.2017.06.226
25
X, Zhang Q, Fang T, Zhang W, Ma G L, Velthof Y, Hou O, Oenema F Zhang . Benefits and trade-offs of replacing synthetic fertilizers by animal manures in crop production in China: a meta-analysis. Global Change Biology, 2020, 26(2): 888–900 https://doi.org/10.1111/gcb.14826
26
D, Chen W, Xing Z, Lan M, Saleem Y, Wu S, Hu Y Bai . Direct and indirect effects of nitrogen enrichment on soil organisms and carbon and nitrogen mineralization in a semi-arid grassland. Functional Ecology, 2019, 33(1): 175–187 https://doi.org/10.1111/1365-2435.13226
27
J, Zhang J, Wang C, Müller Z Cai . Ecological and practical significances of crop species preferential N uptake matching with soil N dynamics. Soil Biology & Biochemistry, 2016, 103: 63–70 https://doi.org/10.1016/j.soilbio.2016.08.009
28
J, Shen Q, Zhu X, Jiao H, Ying H, Wang X, Wen W, Xu T, Li W, Cong X, Liu Y, Hou Z, Cui O, Oenema W J, Davies F Zhang . Agriculture Green Development: a model for China and the world. Frontiers of Agricultural Science and Engineering, 2020, 7(1): 5–13 https://doi.org/10.15302/J-FASE-2019300
29
T, Zhang Y, Hou T, Meng Y, Ma M, Tan F, Zhang O Oenema . Replacing synthetic fertilizer by manure requires adjusted technology and incentives: a farm survey across China. Resources, Conservation and Recycling, 2021, 168: 105301 https://doi.org/10.1016/j.resconrec.2020.105301
30
Y, Li H, Wang Y, Deng D, Liang Y, Li Z Shen . How climate change and land-use evolution relates to the non-point source pollution in a typical watershed of China. Science of the Total Environment, 2022, 839: 156375 https://doi.org/10.1016/j.scitotenv.2022.156375
