Estimation of the Distribution of Tabebuia guayacan (Bignoniaceae) Using High-Resolution Remote Sensing Imagery

Species identification and characterization in tropical environments is an emerging field in tropical remote sensing. Significant efforts are currently aimed at the detection of tree species, of levels of forest successional stages, and the extent of liana occurrence at the top of canopies. In this paper we describe our use of high resolution imagery from the Quickbird Satellite to estimate the flowering population of Tabebuia guayacan trees at Barro Colorado Island (BCI), in Panama. The imagery was acquired on 29 April 2002 and 21 March 2004. Spectral Angle Mapping via a One-Class Support Vector machine was used to detect the presence of 422 and 557 flowering tress in the April 2002 and March 2004 imagery. Of these, 273 flowering trees are common to both dates. This study presents a new perspective on the effectiveness of high resolution remote sensing for monitoring a phenological response and its use as a tool for potential conservation and management of natural resources in tropical environments

Modelling coral reef habitat trajectories : Evaluation of an integrated timed automata and remote sensing approach

The rapid degradation of many reefs worldwide calls for more effective monitoring and predictions of the trajectories of coral reef habitats as they cross cycles of disturbance and recovery. Current approaches include in situ monitoring, computer modelling, and remote sensing observations. We aimed to combine these three sources of information for Abore Reef in New Caledonia by using: (1) a generic timed automata model of reef habitat trajectories, (2) two high spatial resolution multispectral images acquired before and after hurricane Erika in a 2-year interval (March, 2003), and (3) extensive field data on Abore's benthic community structure. Field and remote sensing observations were used to verify model predictions of habitat evolution during the 2-year interval. We also tested whether a fairly generic model of habitat evolution can be used to flag local incorrect image change detection interpretation. The automaton manipulates objects such as states, transitions and clocks (transition times), and we found that it is possible, with expert knowledge, to describe complex habitat trajectories with this formalism. On Abore Reef, we analyzed 22 heterogeneous polygons mapped before and after hurricane Erika using a 36 habitat typology. We examined 75 trajectories suggested by the before-after image classifications and critically reviewed the benefits of the combined timed automata model-image approach. The Abore Reef case study confirms that this is a fruitful path to maximize the benefits of both tools, and minimize their respective drawbacks. However, we conclude that timed automata and remote sensing analysis need to be locally optimized to achieve useful results, and suggests further improvements by using hybrid models able to manipulate continuous, and fuzzy, properties

The next step in shallow coral reef monitoring: Combining remote sensing and in situ approaches

Most current coral reef management is supported by mapping and monitoring limited in record length and spatial extent. These deficiencies were addressed in a multidisciplinary study of cyclone impacts on Abore Reef, New-Caledonia. Local knowledge, high thematic-resolution maps, and time-series satellite imagery complemented classical in situ monitoring methods. Field survey stations were selected from examination of pre- and post-cyclone images and their post-cyclone coral communities documented in terms of substrata, coral morphologies, live coral cover, and taxonomy. Time-series maps of hierarchically defined coral communities created at spatial scales documenting the variability among communities (29-45 classes) and suggesting the processes that affected them. The increased spatial coverage and repeatability of this approach significantly improved the recognition and interpretation of coral communities' spatio-temporal variability. It identified precise locations of impacted areas and those exhibiting coral recovery and resilience. The approach provides a comprehensive suite of information on which to base reef-scale conservation actions. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved

Live Coral Cover Index Testing and Application with Hyperspectral Airborne Image Data

Coral reefs are complex, heterogeneous environments where it is common for the features of interest to be smaller than the spatial dimensions of imaging sensors. While the coverage of live coral at any point in time is a critical environmental management issue, image pixels may represent mixed proportions of coverage. In order to address this, we describe the development, application, and testing of a spectral index for mapping live coral cover using CASI-2 airborne hyperspectral high spatial resolution imagery of Heron Reef, Australia. Field surveys were conducted in areas of varying depth to quantify live coral cover. Image statistics were extracted from co-registered imagery in the form of reflectance, derivatives, and band ratios. Each of the spectral transforms was assessed for their correlation with live coral cover, determining that the second derivative around 564 nm was the most sensitive to live coral cover variations(r2 = 0.63). Extensive field survey was used to transform relative to absolute coral cover, which was then applied to produce a live coral cover map of Heron Reef. We present the live coral cover index as a simple and viable means to estimate the amount of live coral over potentially thousands of km2 and in clear-water reefs