近30多年江苏省滨海淤长型滩涂中农业/渔业用地动态

Dynamics of Agricultural/Aquacultural Lands in Agradational Littoral Beaches in Jiangsu Province in Recent30 Years

以4期(1980年前、1990年前后、2002年和2010年)Landsat遥感影像为基础数据,研究了近30多年来江苏省滨海淤长型滩涂中,农业和渔业用地面积消长、土地的去向及来源变化情况。研究表明,从1980年前至2010年,农业用地面积从436.56km2增长至909.31km2;渔业用地面积从31.67km2增长至838.94km2。其中,农业用地与渔业用地面积在前20a增长相对较快;但近10a来,随着天然湿地提供的土地资源被逐渐消耗,农业/渔业用地面积增长趋缓。在典型淤长型滩涂中,天然湿地被开垦为农业/渔业用地后,很少会再恢复为天然湿地;在过渡型淤长滩涂中,近10a来,恢复为天然湿地的农业/渔业用地比例分别达到了18.10%和13.44%。经过近30多年的围垦,天然湿地比例从74.59%下降为50.30%,芦苇(Phragmites australis)沼泽、碱蓬(Suaeda sp.)沼泽等天然湿地转化为农业/渔业用地趋势减弱。

The agricultural/aquacultural reclamation of aggradational littoral beaches has provided great economic benefits and vast amount of land resources for Jiangsu province in recent 30 years. Most of the coastal wetlands are the aggradational littoral beaches in Jiangsu province. The aggradational littoral beaches in Jiangsu province could be classified to typical aggradational littoral beaches （from Doulong Harbor to Dongzao Harbor）, which aggrades both horizontally and vertically; and transitional aggradational littoral beaches （from Sheyang estuary to the Doulong Harbor, and Haozhi Harbor to Qidongzui）, which aggrades vertically, but erodes horizontally in low tide flat. To improve the development strategy of agriculture/aquaculture in the aggradational littoral beaches, the area variations, fate and source of agricultural/aquacultural lands of the aggradational littoral beaches in the recent 30 years were studied, based on 4 periods （respectively, before 1980, around 1990, 2002 and 2010） of Landsat images. The results showed that the total area of aggradational littoral beaches in Jiangsu province has increased from 2 100.18 km2 to 3 686.31 km2, the area of agricultural lands increased from 436.56 km2 to 909.31 km2, and that of aquacultral lands increased from 31.67 km2 to 838.94 km2 in recent 30 years. In typical aggradational littoral beaches, the agricultural land increased proportionally with the expansion of wetlands, and the percentage of agricultural land in each period was larger than the percentage of aquaculutural land： the area percentages of agricultural land in four periods were 20.79%, 27.12%, 24.95% and 24.67%, respectively; the area percentages of aquacultural land in 4 periods were 0.36%, 7.49%, 19.15% and 22.23%, respectively. In the transitional aggradational littoral beaches, much more lands were reclaimed for aquaculture than for agriculture in the last three decades, the area percentages of agricultural land in 4 periods were 4.97%, 4.30%, 3.97% and 13.01%, respectively; while the area percentages of aquacultural land in 4 periods were 5.73%, 6.74%, 31.56% and 26.54%, respectively. After intensive reclamation in recent 30 years, the proportion of natural wetland decreased from 74.59% to 50.30%, as well as the tendency of natural marshes （such as Phragmites australis community, Saueda sp. community） transmitted to agricultural/aquacultural lands weakened.