Ecological Monitoring
Introduction
It is important that progress in conserving London's biodiversity should be monitored. This is not only to inform the review and refinement of the individual action plans and actions, but also to measure whether or not the action plans are delivering improvements in our quality of life.

There is national advice on biodiversity indicators for sustainable development and quality of life.
Locally, the London Planning Advisory Committee collated indicators for the State of the Environment Report, and many Local Agenda 21 partnerships have suggested indicators. Much of this work was reviewed by the London Ecology Unit in 1996, and that report should be consulted for a fuller account of the subject.

The London Biodiversity Action Plan is designed to include all of the most important wildlife habitat, and most individual species are covered through these habitat plans, rather than through individual species plans. Wildlife habitat is, by definition, indicative of biodiversity in general. The first priority, therefore, is the monitoring of wildlife habitat.
Habitat survey
The best way to monitor most habitat is through comprehensive ground survey of the habitats, as was undertaken by the GLC in 1984/85 and in re-survey of many individual London Boroughs since then. When areas are re-surveyed, the results provide a detailed account of losses and gains. However, such work is expensive and time-consuming, and is likely to be undertaken on a rolling programme, in which each area is revisited at intervals of several years. Some habitats, such as gardens, cannot be surveyed in this way, but can be done by involving members of the public.

Wildlife sites
Changes in the number and area of Sites of Importance for Nature Conservation form one of the indicators in the State of the Environment Report. Without systematic re-survey, however, this indicator is biased - losses are more readily detected than the gains. To help avoid difficulties, this indicator should be compiled by an expert group.

Priority and opportunity habitat
If resources for habitat survey are limited, priority may be given to the irreplaceable habitats, described by English Nature as 'critical natural capital'. In London, the priority would be to monitor Sites of Metropolitan Importance for nature conservation. Where habitats are already monitored by a statutory agency there is an opportunity to develop an indicator at little extra cost. The prime example of this is the river water quality monitoring undertaken by the Environment Agency.

Trees
A special case is the monitoring of trees that is undertaken by some London Boroughs, and the possible repetition of the 'Task Force Trees' study of the early 90s. Unfortunately these data do not provide a complete, unbiased inventory of trees and so they cannot be recommended as an indicator of wildlife habitat.

Monitoring the direct effect of the actions
It is considerably easier to monitor the state of the habitat, or of particular target species, in the places where actions have been undertaken. This is useful for measuring whether or not the actions are locally effective, and so is a desirable detail of biodiversity action.

Monitoring species groups
A group of species can be studied with an efficient census. Changes in numbers or abundance of particular species draw our attention to the need to check what is going on.

Such surveillance is best done through organising the efforts of interested individuals. There is a spectrum of methods ranging from widespread public participatory schemes, like the garden wildlife monitoring undertaken by London Wildlife Trust with postcards and on their website. Another such scheme might be based upon amphibia in London's garden ponds. At the other end of the spectrum are schemes like the Breeding Birds Survey, butterfly transects, the National Bat Monitoring Programme, Wetland Bird Survey and the 'Standard Walk' being piloted in London; schemes designed for use by dedicated amateur naturalists. Surveillance schemes are a cost-effective way of monitoring.

Atlas work
The repetition of work for distribution atlases documents large scale and long-term changes in species distribution. The method is unsuitable, however, for smaller changes in abundance and changes occurring between the repetitions of atlas studies.

Monitoring schemes for individual species
Some individual species are suitable subjects for monitoring. The traditional methods for this again involve trained amateurs undertaking standardised methods. London examples include the long-running heronries survey and the pilot pipistrelle bat survey. Care is needed, however, that multiplication of such single species efforts does not dissipate the resources of London's trained amateurs and detract from the priority for surveillance.

Individual and inadvertent monitoring
Biological recording schemes collect data for reasons other than monitoring, indication or surveillance (see the section on biological records). Much of this information is difficult to employ for monitoring, because the essential requirement, that the effort can be repeated with confidence at some later date, is not met. There are exceptions to this, however, most of which are for species that are readily found if present and are popular with recorders (generally the rarer species in popular groups like birds, butterflies, amphibia, reptiles, bats and higher plants).

Participation
Surveys can be used purely to educate and raise awareness. Participation in monitoring schemes is an excellent way of involving the public in the action plan process. This participation can be organised so that the results provide a repeatable measure, as in the advice above.

Objectives, Actions and Targets

Objective: To employ, encourage, develop and maintain long-term monitoring schemes for London's wildlife habitats and species, to indicate the status of London's biodiversity.

Target: Begin implementing various monitoring schemes and methods by 2002.