Analysing the dynamics and relative influence of variables affecting ecosystem responses using functional PCA and boosted trees: a seagrass case study

1. Understanding the relative influence of variables on ecosystem responses and the dynamics of their effect is necessary for effective ecosystem monitoring and management. Also known as causal pathways anlaysis, we develop an approach using functional Principal Components Analysis (fPCA) and machine learning within a scenario analysis framework.
2. fPCA is used to identify most influential variables for correlated, non-homogenoeus and non-linear time series data characteristic of complex ecosystems. Hierarchical clustering of fPCA scores reveals groups of more homogeneous scenarios and similarly influential variables. The resultant subset of variables helps to overcome model identifiability problems when analysing time-lagged effects using Boosted Regression Trees (BRT).
3. We use simulated data generated by a Dynamic Bayesian Network (DBN) of ecological windows for seagrass ecosystems given dredging stressors; 3024 scenarios with 75 state variables are analysed. The BRT demonstrated...