PARENT SESSION
Poster Session 18: Statistics
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Change detection in ecological observations.

CAPILLA, CARMEN^*,1, ¹ UNIVERSIDAD POLITÉCNICA, VALENCIA, SPAIN

ABSTRACT- Ecological monitoring provides early warning of system changes which may be due to episodic events, environmental stressors or activities impact. These effects frequently modify the central tendency of ecological characteristics by a step change, impulse, monotonic trends or non-stationary trends. The detection and assessment of changes allows determining whether the ecosystem is improving or deteriorating. They help decision-making to introduce corrective actions in order to improve the system. In this paper the application of statistical methods for change detection is illustrated with several ecological datasets. First two univariate temporal datasets are considered. In both cases graphical and numerical techniques are applied. The former are useful for preliminary visualization of changes. Non-parametric and parametric numerical methods are compared to detect and estimate the changes. In the first series a nonlinear trend is analyzed. The second series is a long-term record of observations in a coral reef and exhibits a change in the linear trend. In the last part of the work a multivariate ecological dataset is considered. In many ecosystems it is required to monitor multiple quality indicators. Methods for detecting and analyzing step level shifts and sporadic changes in this last set are used.

Key words: Ecological monitoring, Change detection, Trend analysis