Assessing ecological responses to environmental change using statistical models

Ferguson, C.A., Carvalho, L., Scott, E.M. , Bowman, A.W. and Kirika, A. (2008) Assessing ecological responses to environmental change using statistical models. Journal of Applied Ecology, 45(1), pp. 193-203. (doi: 10.1111/j.1365-2664.2007.01428.x)



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There is a clear need to improve our ability to assess the ecological consequences of environmental change. Because of the complexity of ecosystems, predictions are often reliant on models and expert opinion. These require validation with observed data; in this respect, long-term data sets are particularly valuable. Innovative statistical methods are presented for identifying ecological trends and changes in seasonality in response to environmental change. These are illustrated through the example of Loch Leven, a shallow freshwater lake. 35 years of monitoring data are examined spanning periods of enrichment, ecological recovery and changing climate. The use of additive models are illustrated for assessing non-monotonic annual trends and seasonal variability of responses, often typical of noisy and complex ecological time-series. Nonparametric regression models are used to consider seasonal trends and to investigate if seasonal patterns change throughout time. Models are developed for phosphorous and nitrogen; temperature and rainfall; <i>Daphnia</i> grazers and chlorophyll<sub>a</sub>. The analysis highlights a generally decreasing availability of phosphorous over the study period and generally increasing nitrate concentrations and rainfall. Increasing spring temperatures are also evident. There have been no significant trends in annual mean grazer densities for the period 1971-2002. Significant changes in summer grazer densities were highlighted, with a decreasing trend until the early 1990s, followed by an increasing trend to 2002. Chlorophyll<sub>a</sub> models indicated significant declining trends for the period 1968-2002, driven largely by significant reductions in spring and summer early on in the first three years. Seasonality also changed, with a reduced and earlier spring peak and a more prominent "clear water" period in late spring/early summer. These changes may be driven by the observed increasing trend in spring temperatures and consequent increasing spring <i>Daphnia</i> densities. <i>Synthesis</i> <i>and</i> <i>applications</i>: The analysis highlights the value of statistical models for assessing complex ecological responses to environmental change. The models outlined can examine key ecological impacts of climate change, particularly effects on the timing of seasonal events and processes.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Scott, Professor Marian and Bowman, Prof Adrian and Miller, Professor Claire
Authors: Ferguson, C.A., Carvalho, L., Scott, E.M., Bowman, A.W., and Kirika, A.
Subjects:Q Science > QA Mathematics
G Geography. Anthropology. Recreation > GE Environmental Sciences
College/School:College of Science and Engineering > School of Mathematics and Statistics > Statistics
Journal Name:Journal of Applied Ecology
Copyright Holders:Copyright © 2008 Blackwell
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher.

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