Determining historic ecological conditions in lowland rivers: applying palaeoecological techniques to river restoration planning

人们普遍认识到，人类活动已导致全球河流生态系统的水文形态（水流特征和河流地貌）和生态发生重大变化，在许多情况下可能需要恢复形态多样性的河流物理恢复。然而，重要的问题仍然是关于河流的植物群和动物群的性质和数量已经失去了或不利的历史通道修改整个低地英格兰。这些河流中的许多已经被广泛修改了许多世纪，用于各种目的。一些最重要的变化发生在第二次世界大战后的几十年里，通过改善土地排水和相关的洪水管理来提高粮食安全。包括拉直、加深、拓宽和重新配置的植被化导致栖息地异质性大大降低，对河流和洪泛区生物多样性产生严重影响。需要更好地了解地貌、水文、特别是已受到损害或丧失的生物多样性要素，以便充分利用计划采取的恢复和恢复河道形态和功能的措施的好处。要产生这种理解的环境中的自然过程已经在大的空间尺度上的影响，提出了一种创新的古生态方法，将提供一个窗口，在过去的河流条件，使当代的通道和社区居住，它可以测量恢复之前。该项目将结合联合收割机分析当代河流形态和生态与古生态学技术（通过检查与河流相关的沉积物和河漫滩沉积物），探索英格兰选定的低地河流的近代历史。我们假设，自然元素的通道形态和instantaneous动物群落已丢失或妥协，由于历史的管理实践。该项目将通过使用古生态学技术，通过检查化石和当代毛翅目（石蛾幼虫）和水生鞘翅目（甲虫）组合，查明一些受到改变的重要生境特征，并查明动物群落的变化。研究地点是从被指定为具有特殊科学价值地点（SSSIs）的英国河流网络中选择的。该网络包括在英格兰发现的不同河流类型的代表性例子，研究将集中在六条河流上，包括：Beult河（肯特），R。Eye（Leicestershire），R.船体（东约克郡）和R. Wensum（诺福克）都表现出不同程度的变直和过度增宽，而R. Mease（Staffordshire）的改良显著较少，而R. Blythe（W. Mids.）其具有很大程度上未修改的通道形式。潜在的古河道地点已确定追溯到战后时代的渠道修改。这些包括古老的河道特征（包括河道拉直后切断的河曲或天然牛弓）或基本上经过改造的河道内未受干扰的沉积物。详细的地点确定将涉及审查历史地图，河流的地貌评价，航空照片的研究和咨询当地自然英格兰和环境局的工作人员。将按照拉夫堡大学制定的程序收集和分析沉积物芯和/或切片，以寻找大型无脊椎动物亚化石（毛翅目和鞘翅目）。这些数据将与当代修改后的通道中记录的社区进行比较，以直接评估可能因地貌改变而产生的变化。

It is widely recognised that anthropogenic activities have resulted in significant changes to the hydromorphology (flow characteristics and fluvial geomorphology) and ecology of riverine ecosystems globally and that to reinstate morphological diversity physical river restoration may be required in many instances. However, significant questions remain regarding the nature and number of riverine flora and fauna that have been lost or disadvantaged by historic channel modifications across much of lowland England. Many of these rivers have been extensively modified for many centuries for a variety of purposes. Some of the most significant modification took place in the decades following World War II, in a drive to increase food security through improved land drainage and associated flood management. Channelisation, involving straightening, deepening, widening and reprofiling resulted in greatly reduced habitat heterogeneity, with serious implications for riverine and floodplain biodiversity. A better understanding of the geomorphological, hydrological and particularly the biodiversity elements that have been compromised or lost is required in order to characterise the benefits of planned measures to restore and reinstate channel form and function. To generate this understanding in an environment where natural processes have been impacted over large spatial scales, an innovative palaeoecological approach is proposed that will provide a window on past riverine conditions so that the contemporary channel and community inhabiting it can be gauged prior to restoration. This project will combine analysis of contemporary river morphology and ecology with palaeoecological techniques (via examination of instream and floodplain deposits associated with the river) to explore the recent history of selected lowland rivers in England. We hypothesise that natural elements of channel morphology and the instream faunal community have been lost or compromised due to historic management practices. The project will characterise some of the critical habitat features that have suffered from modifications and through the use of palaeoecological techniques characterise the changes in the faunal community through examination of fossil and contemporary Trichoptera (caddis fly larvae) and aquatic Coleoptera (beetles) assemblages. Study sites have been selected from the English network of rivers designated as Sites of Special Scientific Interest (SSSIs). This network includes representative examples of different river types found in England and research will focus on six rivers comprising: the River Beult (Kent), R. Eye (Leicestershire), R. Hull (EastYorkshire) and R. Wensum (Norfolk) all exhibiting straightening and over-widening to varying degrees, and the R. Mease (Staffordshire) with significantly less modification and the R. Blythe (W. Mids.) which has a largely unmodified channel form. Potential palaeochannel localities have been identified dating from the post-war era of channel modification. These include old channel features (including meanders cut off following channel straightening or natural ox-bows) or sediments within largely modified channels that have escaped disturbance. Detailed site identification will involve examination of historical maps, geomorphological appraisals of the rivers, study of aerial photos and consultation with local Natural England and Environment Agency staff. Sediment cores and/or sections will be collected and analysed for sub-fossil macroinvertebrates (Trichoptera and Coleoptera) following the procedures developed at Loughborough University. This data will be compared with the communities recorded in the contemporary modified channel, in order to directly evaluate changes likely to have resulted from the altered geomorphology.