Data from: Signatures of human impact: size distributions and spatial organization of wetlands in the prairie pothole landscape

More than 50% of global wetland area has been lost over the last 200 years, resulting in losses of habitat and species diversity as well as decreased hydrologic and biogeochemical functionality. Recognition of the magnitude of wetland loss as well as the wide variety of ecosystem services provided by wetlands has in recent decades led to an increased focus on wetland restoration. Restoration activities, however, often proceed in an ad-hoc manner, with a focus on maximizing the total restored area rather than on other spatial attributes of the wetland network, which are less well understood. In this study, we have addressed the question of how human activities have altered the size distribution and spatial organization of wetlands over the Prairie Pothole Region of the Des Moines Lobe using high-resolution LIDAR data. Our results show that as well as the generally accepted 90% loss of depressional wetland area, there has been a disproportionate loss of both smaller and larger wetlands, with a marked alteration of the historical power-law relationship observed between wetland size and frequency and a resulting homogenization of the wetland size distribution. In addition, our results show significant decreases in perimeter-to-area ratios, increased mean distances between wetlands, particularly between smaller wetlands, and a reduced likelihood that current wetlands will be located in upland areas. Such patterns of loss can lead to disproportionate losses of ecosystem services, as smaller wetlands with larger perimeter-to-area ratios have been found to provide higher rates of biogeochemical processing and groundwater recharge, while increased mean distances between wetlands hinder species migration and thus negatively impact biodiversity. These results suggest the need to gear restoration efforts towards understanding and recreating the size distribution and spatial organization of historical wetlands, rather than focusing primarily on an increase in overall area.

过去200年间，全球已有超过50%的湿地面积消失，由此引发栖息地丧失、物种多样性下降，同时削弱了湿地的水文与生物地球化学功能。近几十年来，随着学界对湿地流失严重程度的认知不断加深，以及对湿地所提供的多样化生态系统服务的重视程度提升，湿地修复相关研究与实践的关注度持续走高。然而，当前湿地修复活动往往以零散随意的方式开展，仅追求修复总面积的最大化，却忽视了湿地网络中其他更难被量化与认知的空间属性。本研究借助高分辨率激光雷达（LIDAR）数据，针对得梅因冰碛舌草原坑洼区域（Prairie Pothole Region of the Des Moines Lobe）内人类活动如何改变湿地规模分布与空间组织格局这一问题展开了探究。研究结果显示，除学界普遍认可的洼地湿地面积损失达90%之外，小型与大型湿地均出现了不成比例的流失，湿地规模与出现频率间原本的经典幂律（power-law）关系发生了显著改变，最终导致湿地规模分布趋于同质化。此外，研究还发现湿地的周长面积比显著降低，湿地间的平均距离有所增加，尤其是小型湿地之间的平均距离增幅更为明显，且当前湿地分布在高地的概率有所下降。这类流失模式会引发生态系统服务的不成比例损失：已有研究证实，周长面积比更高的小型湿地具备更强的生物地球化学循环速率与地下水补给能力，而湿地间平均距离的增加会阻碍物种迁移，进而对生物多样性产生负面影响。上述研究结果表明，湿地修复工作应转向理解并复刻历史湿地的规模分布与空间组织格局，而非仅关注修复总面积的提升。