MONITORING TRENDS IN BIODIVERSITY
Present patterns in global biodiversity reflect the many and extensive changes brought about by the human species. No natural habitats are free from human impact, and large areas have been totally transformed. Many wild species have declined in distribution and abundance; some are known to have become extinct. With human help, domestic livestock and crops occupy large areas of land, along with introduced game animals and a host of accidental introductions, including many weeds and animal pests.
The objectives of the Convention are to conserve biodiversity, to use its components sustainably, and to ensure that benefits arising from the use of genetic resources are shared equitably. Core tasks, as set out in Article 7 of the Convention, are to identify important components of biodiversity and to monitor trends in their status. While it is usually feasible to assess national biodiversity at a general level in terms of species and broad ecosystem types, and this is evident in the national reports submitted to the Secretariat (see chapter 4), effective monitoring is a greater challenge.
Monitoring implies repeated assessment in order that change and long-term trends over time can be identified. All kinds of evidence may be admissible, but for scientific dialogue a quantitative and structured monitoring framework is preferred, and for comparative purposes, for example seeking to build a comprehensive continental or global picture from national data, it is desirable that similar parameters are measured in similar terms. Until recently, however, change in biodiversity at species and habitat level has very often been identified retrospectively on an
ad hoc basis, by means of largely anecdotal evidence, and using terms and units of measurement that are highly case-specific.
Knowledge of biodiversity at local and regional levels is embedded in cultural practices and languages. The knowledge, innovations and practices of indigenous and local communities are key human components of sustainability. They are the result of long periods of use, observation and experimentation. The decline of cultural diversity brings with it the concomitant loss of biodiversity knowledge. This is especially the case when languages are lost.
During the past decade, considerable effort has been devoted to the assessment of change in the environment, often at national or regional level, and to the development of indicators to represent environmental change. An indicator is a value, perhaps an index derived from a set of observational data, that can be taken to represent some broader issue beyond the indicator value itself. The central purpose is to communicate real-world complexity in a simplified and readily understood numerical or graphic form.
Economic indicators rely mainly on time-series of quantitative numerical data, as do the most effective environmental indicators, for example those relating to trends in readily measurable factors such as temperature or carbon dioxide emissions. One of the principal obstacles to the development of good biodiversity indicators is that time-series of numerical data, especially if applicable above local or national level, are scarce. For this reason, most existing biodiversity indicators are based on static status assessments, for example the proportion of the mammal fauna that is threatened with extinction, the number of national-endemic species, or amount of protected forest.
Now that a large number of countries have begun to implement the Convention, and the period since relevant measures have been in place is lengthening, it is increasingly desirable to develop tools to monitor the actual on-the-ground impacts of compliance. The Parties have explicitly recognized this need in their several calls for development of a core set of biodiversity indicators, and in their efforts to improve and harmonise national reporting.
However, it is not yet possible to build a reliable and comprehensive picture of the effectiveness of measures adopted in compliance with the CBD, in terms of change in the status of the components of biodiversity. This is in part because insufficient time has passed since implementation of the Convention at national level began so that it is in many instances not realistic to expect a clear response, i.e. recovery or restoration of species and habitats is generally a protracted process. It is in part also because reliable monitoring tools, with the appropriate resolution, have not been developed and widely implemented.
