Hertfordshire’s Ecological Networks A report on the current situation and priorities for restoration Hertfordshire’s Ecological Networks Page 1 of 51 Contents Foreword ................................................................................................................................................. 4 Acknowledgments ................................................................................................................................... 5 1 Executive summary .............................................................................................................................. 6 2 Introduction ......................................................................................................................................... 7 2.1 Background ................................................................................................................................... 7 2.2 Summary of the historical context of Hertfordshire’s natural environment ................................ 8 2.2.1 Woodlands ............................................................................................................................. 9 2.2.2 Grasslands ............................................................................................................................ 12 2.2.3 Wetlands .............................................................................................................................. 14 2.3 Summary of Hertfordshire’s present natural environment ........................................................ 17 2.3.1 Hertfordshire’s physical geography ..................................................................................... 18 2.3.2 Hertfordshire in the context of National Character Areas (NCAs) ....................................... 20 2.3.3 Herts Chilterns (part of NCA 110 – Chilterns) ...................................................................... 22 2.3.4 Northern Herts Chalk (part of NCA 87 – East Anglian Chalk) ............................................... 23 2.3.5 Upper Colne Valley (part of NCA 115 – Thames Valley) ...................................................... 24 2.3.6 Hornbeams and Heaths (part of NCA 111 – North Thames Basin) ...................................... 25 2.3.7 Eastern Herts Clayland (part of NCA 86 - South Suffolk & North Essex Clayland) ............... 26 2.3.8 North-West Clay Vale (part of NCA 88 - Bedfordshire and Cambridgeshire Claylands) ...... 27 2.4 Project purpose ........................................................................................................................... 27 3 Methods ............................................................................................................................................. 28 3.1 Producing the habitat inventory ................................................................................................. 28 3.2 Modelling ecological networks ................................................................................................... 28 3.3 Identifying landscape-scale ecological units ............................................................................... 30 3.4 Combining all the outputs into a single GIS dataset ................................................................... 32 4 Results ................................................................................................................................................ 33 4.1 Habitat inventory ........................................................................................................................ 33 Hertfordshire’s Ecological Networks Page 2 of 51 4.2 Ecological networks .................................................................................................................... 35 4.3 Landscape-scale ecological units ................................................................................................ 41 4.3.1 Chalk strategic core areas .................................................................................................... 42 4.3.2 Acidic strategic core areas ................................................................................................... 43 4.3.3 Wetland strategic core areas ............................................................................................... 44 4.3.4 Strategic core areas in relation to National Character areas ............................................... 44 4.4 A single combined GIS dataset .................................................................................................... 45 5 Conclusions and further remarks ....................................................................................................... 47 5.1 The state of Hertfordshire’s ecological networks ....................................................................... 47 5.2 Where to prioritise efforts .......................................................................................................... 47 5.3 Choosing between different habitats to create .......................................................................... 48 5.4 Interpreting general patterns in ecological networks ................................................................ 48 5.5 Uses of the habitat network maps .............................................................................................. 49 5.6 Limitations in relation to soil and hydrological data................................................................... 49 5.7 Using this report in conjunction with other reports ................................................................... 49 6 References ......................................................................................................................................... 51 Hertfordshire’s Ecological Networks Page 3 of 51 Foreword The United Kingdom has a long history of protecting and conserving the natural environment and, for many years, a wide variety of organisations and individuals have been committed to this objective including Government Agencies, Local Authorities, Non-Governmental Organisations, local community groups, and dedicated individual members of the public. However, in recent years, a succession of reports (including the Lawton Review, the Natural Environment White Paper and the 2013 State of Nature report) have all clearly shown that, despite the best efforts of all concerned, both the health of our ecosystems and their ability to function properly are continuing to deteriorate. Looking ahead, the challenges posed by climate change, combined with an increasing human population and growing concerns about the security of food supplies, are likely to exacerbate these pressures upon the natural environment. At the same time, the National Ecosystem Assessment has emphasised just how essential it is for our ecosystems to be healthy and fully functional, in order to support our own health, growth and prosperity. Healthy and functional ecosystems and networks are also generally accepted to be more resilient to the impacts of external influences such as climate change. One of the most important recommendations from the Lawton Review is that the traditional approach of protecting and conserving individual existing sites is no longer sufficient; instead we need to adopt a landscape- scale approach of restoring and creating habitats around and between those existing sites; in order to increase resilience, quality and connectivity of habitats. In response to this conclusion, a number of landscape-scale initiatives, most notably the Nature Improvement Areas, have been launched to address the restoration and creation of these wider habitat networks. However, in this crowded island of ours, almost every piece of land is subject to a range of conflicting pressures and potential uses. This is especially the case in a relatively small and heavily populated county such as Hertfordshire. It is therefore vitally important that local authorities and other decision-makers should be equipped with the best possible environmental information upon which to base their decisions. In particular, before committing increasingly scarce resources to the restoration or creation of an area of habitat, it is important that we should be sure that it will be ‘the right habitat in the right place’; offering the best possible prospects for successful habitat establishment and the highest environmental return from the resources invested. The production of this new Hertfordshire habitat inventory and series of potential habitat network maps is therefore particularly timely. On behalf of Natural England, I welcome this report and congratulate its authors on their achievement. I hope that local authorities and other decision- makers will make good use of the habitat inventory and the potential habitat network maps and will find them to be valuable tools in their work to conserve the best features of Hertfordshire, whilst at the same time seeking to create an even better Hertfordshire for future generations. Gordon Wyatt, Lead Advisor (Land Use Operations), Natural England Hertfordshire’s Ecological Networks Page 4 of 51 Acknowledgments This was a Local Nature Partnership (LNP) project, led by Herts & Middlesex Wildlife Trust. Funding was provided by Herts & Middlesex Wildlife Trust and Hertfordshire County Council. Part of the project was also funded by Natural England, in relation to the area covered by the Lea Catchment Nature Improvement Area (NIA). The project was identified within the