Common use of Population trend Clause in Contracts

Population trend. Description of the direction and rate of change in population size (i.e. trend) is the other fundamental attribute used to assess the status of a species or population at site, national or flyway scales. However, both the length of the trend period and the trend classification depends on the purpose of the analysis and data availability. Ideally, trends are based on annual data for better statistical power, but less frequent (ideally not less frequent than once in every 3 years) data collection might be acceptable if establishing the trend would require very extensive surveys. Trend periods can be: i. A fixed moving time period (typically the last 5, 10 or 25 years) used to characterise the current (i.e. most recent short-term) or long-term trend. The current trends can be used as an early warning, while the long-term trends are less influenced by short-term fluctuations. This makes them more robust but also less sensitive. The long-term trend could indicate a problem too late if a population for example recovered at some point in the time series, but then declined again. ii. Linked to some policy-relevant benchmark, e.g. 1980 is used both for the EU Article 12 reporting as this is the first full year after the Birds Directive came into force. (For the sake of consistency, the same start year has been adopted also for the AEWA national population status reporting). The year of designation of a protected area can be used to assess whether the site still holds the numbers it has been designated for. iii. Linked to generation length, e.g. the trend rend over 10 years or 3 generations, whichever is the longer is used by both the IUCN Red List and for the classification of populations on AEWA Table 1 under the criteria 2c and 3c of Columns A and B respectively. The rate of change is often compared to certain pre-set values, either to classify the trend or to use it in alert or trigger systems based on its value and the width of its confidence intervals.