Remote sensing: a key tool for interdisciplinary assessment of coral reef processes

Growing consensus exists among scientists that global climate change really is upon us and is taking an increasingly heavy toll on coral reefs. The scientific literature and conference proceedings abound with reports about impacts. But how bad is the situation really? Are we being misled by small-scale studies that justifiably ring the alarm bell for a specific area without necessarily having relevance for the world at large? Clearly, the immense challenge of understanding the severity and patterns of impacts on coral reefs due to globally changing climate patterns requires tools that allow coherent and speedy investigation of large areas—ranging in size from reef systems to entire ocean basins. Fortunately, over recent decades, remote sensing has developed into an increasingly refined and widely used tool that has found many applications within the coral reef research community. It is with this in mind that the present special issue was conceived. At first glance, the papers published in this special ‘‘Remote Sensing and Coral Reefs’’ issue of Coral Reefs may look like a disparate collection of studies, spanning most coral reef regions worldwide (Pacific, Caribbean, Red Sea, Indian Ocean) using a variety of sensors (SeaWiFS, Landsat, IKONOS, LIDAR, in situ spectrometry), methods (analytical, statistical, empirical, modeling), scales (regional to species-level), and applications related to various reef processes. However, each of these 15 studies is representative of one of the current axes that characterizes the integration of the remote sensing (RS) tool in coral reef science and management. Under the broad label ‘‘coral reef,’’ we accepted submissions for this special issue targeting any subject ranging from individual coral colonies to the largest reef systems (Great Barrier Reef) or carbonate banks (Bahamas). We also expected studies on deeper coral reefs and carpets using acoustic technology but none of the letters of interest were followed by an actual submission, suggesting that more efforts are required to interpret acoustic data in a reef context. The growing body of investigators considering in-water active sensors for deep or shallow surveys beyond the limit of optical remote sensing will certainly justify another compilation of state-of-the art works in the future. We explicitly encouraged submission of papers presenting the integration of remote sensing data into studies addressing reef mega-processes (sensu Hatcher 1997), beyond just methodological development. Eventually, only seven studies revealed new environmental knowledge using relatively standard remote sensing data or practices (Acker et al. 2004; Berkelmans et al. 2004; Hochberg et al. 2004; Otis et al. 2004; Penland et al. 2004; Andréfouët et al. 2004; Naseer et al. 2004). Conversely, eight papers can be primarily qualified as ‘‘methodological’’ since they investigate the potential of new high spatial resolution sensors (Elvidge et al. 2004; Brock et al. 2004), new ways to combine remote sensing and in situ data (Purkis and Pasterkamp 2004; Joyce et al. 2004), and modeling (Ouillon et al. 2004; Wooldridge and Done 2004), and investigate the behavior of spectral measurements of reef benthos as prelude to hyperspectral surveys (Hedley et al. 2004; Karpouzli et al. 2004). Of course, most of these method papers also provide some environmental information, but this is clearly not the primary goal. The environmental knowledge was known beforehand and used to critically S. Andréfouët (&) College of Marine Science, Institute for Marine Remote Sensing, University of South Florida, 140 7th Av. South, St Petersburg, FL 33701, USA E-mail: andrefou@noumea.ird.nc