Spatial and temporal characteristics of agricultural green development indica-tors in Hainan Island

Since the establishment of Hainan Province, the scale, structure, and methods of agricultural production have undergone significant changes, which are critical with respect to the progress of agricultural green development (AGD). In this study we adopted China's AGD indicator system with 20 indicators, and using the NUFER (NUtrient flows in Food chains, Environment and Resources use) model, we quantitatively calculated the spatial and temporal changes in Hainan Island AGD indicators from 1988 to 2017. Moreover, we discussed the factors restricting AGD in Hainan Island. The results revealed that the overall level of Hainan Island's AGD had shown a declining trend over the past 30 years. The numbers of indicators at lower levels (Ⅲ and Ⅳ) had increased from 12 to 15, whereas those at higher levels (Ⅰ and Ⅱ) had decreased from 8 to 5. With increase in the proportion of economic crops such as vegetables and fruits, the scale of livestock and poultry farming and the degree of intensification, Hainan's agricultural output value and social development level had continued to increase. Furthermore, the agricultural output value per unit cultivated land area and level of agricultural mechanization had increased from 6 200 ￥·hm^-2 and 3 kW·hm^-2 to 161 000 ￥·hm^-2 and 13 kW·hm^-2, respectively. Over the past 30 years, there had been an increasingly excessive input of agricultural resources (nitrogen, phosphorus, pesticides, and agricultural film), among which, the intensities of pesticide and agricultural film usage had shown the highest increases, rising from 8.0 kg·hm^-2 and 0 kg·hm^-2 to 41.9 kg·hm^-2 and 34.7 kg·hm^-2, respectively. As a consequence of the low productivity levels, the environmental emissions of applied nutrients (e.g., nitrogen surplus in farmland, nitrogen runoff in farmland, and NH₃ volatilization from agricultural system) had increased significantly, with NH₃ volatilization and nitrogen surplus per unit sown area showing the largest increases, rising from 61.0 kg·hm^-2 and 152.1 kg·hm^-2 to 131.4 kg·hm^-2 and 297.9 kg·hm^-2, respectively. Environmental pollution caused by an excessive input of agricultural resources and the separation of agriculture and animal husbandry had been the main factors contributing to the restriction of AGD in Hainan Island. Given that the central part of the island is covered in montane forest and has been designated as a national key ecological function protection area, the scale of development in this region had been relatively limited. Consequently, the coastal plains had experience more rapid growth in resource input. Although this had a detrimental impact on the environment, the economy growth, social development, and agricultural productivity indicators for these areas had improved to a greater extent than those for mountain forest area. In the future, Hainan Island should rationally optimize the planting structure in coastal areas, improve the level of production management, and strengthen the combination of agriculture and animal husbandry to reduce resource losses and achieve the island's requisite AGD goals.