Chapter 1
Chapter 1
An evidence-based study mapping the decline in freshwater ponds in the Severn Vale catchment in the United Kingdom between nineteen hundred and twenty nineteen.
Abstract Freshwater ponds have long been an overlooked biodiversity store and changing types of land use and the land management practices has led to a steady decline in pond numbers. Establishing the regional extent of pond loss is the first step in identifying key areas for conservation action. This study calculated pond loss in the Severn Vale catchment United Kingdom since nineteen hundred. Identification of pond location and surrounding land use on historic and contemporary maps enabled a comparison of total number, density and distance between present day and historic ponds. Fifty-seven point seven percent of ponds present in nineteen hundred were lost and pond density declined from seven point three to four point five ponds per square kilometer between nineteen hundred and twenty nineteen. This resulted in a twenty-four point six meter increase in the average distance between contemporary ponds. Land use was an important factor in determining pond loss. Although in twenty nineteen the highest density of ponds are in rural areas, sixty-two point three percent of ponds lost were from agricultural settings (arable or pasture). Our results highlight the significant pond loss experienced in the Severn Vale since nineteen hundred and provide a valuable baseline for pondscape restoration. The methods described are widely applicable to other regions either with a history of ponds or an environment that could sustain them.
Introduction
Introduction
In Great Britain ninety-seven percent of standing water bodies are less than two hectares in area. Although individually small they constitute a substantial and valuable freshwater habitat. Understanding the distribution, quality, and heterogeneity of ponds at a pondscape scale is vital for directing practical conservation and restoration efforts. These smaller water bodies support around two-thirds of all wetland plants and animals found in Britain. When compared to other freshwater habitats, ponds support more species of macrophytes and macroinvertebrates, and often outperform lakes and rivers in the number of nationally scarce and IUCN red list species they support. In increasingly managed and homogenous landscapes, these small but rich habitats are important biodiversity hotspots. In addition to their biodiversity value, ponds also provide ecosystem services such as floodwater attenuation, carbon storage, and recreational and aesthetic amenity value. There is also increasing evidence that ponds also support terrestrial species such as farmland birds, bats, and pollinators. Clearly, even though ponds are small features they remain key components of healthy landscapes and the numbers and quality of ponds at national and regional scale should give cause for concern.
In two thousand seven, the total number of ponds in the United Kingdom was estimated at four hundred eighty thousand that collectively covered about one hundred ninety thousand hectares of land. As no standardized inventory of ponds were available these national estimates for Great Britain were generated by counting the ponds in five hundred ninety-one one square kilometer areas, and extrapolated these to calculate a national figure as part of the United Kingdom government's Countryside Survey. Whilst these national estimates are useful for headline indications of present day pond abundance, the data become less pertinent at the smaller, local landscape level, where the number and distribution of ponds is likely to be more idiosyncratic.
In addition to curating present day data on pond abundance and distribution, the value of historic pond data is increasingly being highlighted. Temporal mapping of ponds using historic maps can precisely locate and quantify lost ponds, which is particularly useful to practical pond conservation efforts in several ways. Firstly, by establishing the historic location of individual ponds, we can prioritise locations at which the existing seed bank can be used to facilitate pond establishment. Secondly, by establishing the extent and distribution of pond loss at a landscape scale, we can prioritise areas within the pond network. A large number of historic ponds were anthropogenic in origin, being created for a variety of purposes and therefore have the potential to have strong socio-cultural connections for stakeholders. Mapping historic pond distribution at a landholding scale can therefore also be a useful engagement tool, potentially helping to overcome barriers to pond creation and/or restoration.
The Severn Vale management catchment, hereafter referred to as the Severn Vale, is a diverse landscape of one thousand four hundred eighty-seven square kilometers in the Southwest of England. Examining pond loss at this scale and across a diverse range of habitat types available in the Severn Vale also means the methods developed in this research are readily applicable in other countries and settings that need to accurately assess pond loss.
This study collates the location data for ponds at a regional scale from historic and present day sources and standardizes these data into comparable file formats. Once the historic and present day pond locations and distributions have been established, this study then examines the change in pond number and density. The precise distance between ponds are calculated and compared with land use categorization from both time periods. Together these data establish the key landscape scale temporal changes that have occurred and identify the probable causes of pond loss across the catchment.