Abstract
The monitoring of ecosystem dynamics utilises time and resources from scientists and land-use managers, especially in wetland ecosystems in islands that have been affected significantly by both the current state of oceans and human-made activities. Deep-learning models for natural and anthropogenic ecosystem type classification, based on remote sensing data, have become a tool to potentially replace manual image interpretation. This study proposes a U-Net model to develop a deep learning model for classifying 10 island ecosystems with cloud- and shadow-based data using Sentinel-2, ALOS and NOAA remote sensing data. We tested and compared different optimiser methods with two benchmark methods, including support vector machines and random forests. In total, 48 U-Net models were trained and compared. The U-Net model with the Adadelta optimiser and 64 filters showed the best result, because it could classify all island ecosystems with 93 percent accuracy and a loss function value of 0.17. The model was used to classify and successfully manage ecosystems on a particular island in Vietnam. Compared to island ecosystems, it is not easy to detect coral reefs due to seasonal ocean currents. However, the trained deep-learning models proved to have high performances compared to the two traditional methods. The best U-Net model, which needs about two minutes to create a new classification, could become a suitable tool for island research and management in the future.
Highlights
More than 100,000 islands have 500 million residents in total, encompass 20% of global biodiversity and provide the according sustenance (Muñoz et al 2013)
The total accuracy and loss function values were used to compare the performance of these U-shaped convolutional neural network (U-Net) models (Table 1)
In four types of optimiser methods, the UNet-Stochastic Gradient Descent algorithm (SGD) models had the lowest performance compared to other methods
Summary
More than 100,000 islands have 500 million residents in total, encompass 20% of global biodiversity and provide the according sustenance (Muñoz et al 2013). A sixth of the Earth's surface is covered by island ecosystems and the oceans around them (MEA 2003). These ecosystems support more rare, endangered and vulnerable species than those found on the mainland (Balzan et al 2018). They provide both terrestrial and marine ecosystem services (Laurans et al 2013). The changes in island ecosystems have received great attention from scientists in recent years (McLean et al 2001, Laurans et al 2013)
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