Review: Turner W, Spector S, Gardiner N, Fladeland M, Sterling E, Steininger M (2003) Remote sensing for biodiversity science and conservation. TRENDS in Ecology and Evolution, 18(6):306-314.

Feature Paper: DOWNLOAD Turner W, Spector S, Gardiner N, Fladeland M, Sterling E, Steininger M (2003) Remote sensing for biodiversity science and conservation. TRENDS in Ecology and Evolution, 18(6):306-314.

Author Abstract: Remote-sensing systems typically produce imagery that averages information over tens or even hundreds of square meters – far too coarse to detect most organisms – so the remote sensing of biodiversity would appear to be a fool’s errand. However, advances in the spatial and spectral resolutions of sensors now available to ecologists are making the direct remote sensing of certain aspects of biodiversity increasingly feasible; for example, distinguishing species assemblages or even identifying species of individual trees. In cases where direct detection of individual organisms or assemblages is still beyond our grasp, indirect approaches offer valuable information about diversity patterns. Such approaches derive meaningful environmental parameters from biophysical characteristics that are revealed by remote sensing.

Note to Readers: Follow links above for author email, full article text, or the publishing scientific journal. Author notes in my review are in quotes.

Review: This is the second paper of our 12-week course in biogeography, and the first paper of week 2. We'll review this paper first, followed on Saturday by the second paper. Both of the papers for this week deal with approaches meant to discover, map, and quantify patterns of diversity of various organisms in space.

Remote sensing (the topic of this paper) uses images or data gathered from above an ecosystem or organism as opposed to direct observation and measurement in situ (or in the field). Typically, remote sensing involves either balloons, airplanes, or satellites to capture images of environments and then classify those environments in a variety of ways, which this paper outlines.

The authors define remote sensing, for the terms of their paper, as "the detection of electromagnetic energy from aircraft or satellites" and outline the basics of such systems in an excellent figure (below).

The authors point out that there are three environmental "parameters" often detected through remote-sensing technologies: "primary productivity, climate and habitat structure (including topography)." Other variables listed by the authors that are presently detectable (with varying errors) through remote sensing include: species composition (plants and animals), land cover, chlorophyll (primary productivity), ocean color and circulation, rainfall, soil moisture, phenology, topography, and vertical canopy cover.

The authors list multiple satellites presently used for remote sensing of the environment, with links to each satellite's website. Almost anyone can purchase images produced by such satellites or direct flyovers using specific instruments or parameters for specific regions of the globe.

And while the authors focus on environmental applications, scientists also use remote sensing equipment to detect human encroachment on the environment or to track devastation following natural disasters.

The authors discuss how increases in satellite resolution, coupled with increases in the ability to detect specific spectra along electromagnetic wavelengths and how spectral discrimination of certain plant and animal species has allowed "species-specific land-cover classification from the use of airborne and spaceborne" instruments.

Perhaps the greatest asset of remote sensing is the ability to map and classify large tracks of land, coastal, or aquatic regions and follow changes in their composition over time.

The authors go through the various parameters discussed above and deal with the specific satellites, airplanes, helicopters, etc. and instruments that have been useful thus far in collecting data of various types as outlined above. For anyone thinking about a project involving remote sensing of a specific type of data, I recommend referencing the article section on the remote-sensing instrument you intend to use, as the authors do a good job of outlining the resolutions, accuracies, type of data available from each instrument, and several examples of how each instrument is used presently.

Despite the advantages of remote-sensing (especially for remote areas that are difficult for scientists to access, or as compliments to small-scale surveys that can be expanded regionally using remote sensing coupled with ground trotting) there are still "major challenges involved in working with remote-sensing data." The authors outline the following:

• "Costs for imagery and other data products are often high"
• "Handling even small quantities of satellite imagery requires special software and hardware tools."
• "The technical expertise required to handle imagery and other data products [involve] training and hours spent working with the imagery [as] a prerequisite for understanding what one is looking at."
• "Many of the remote-sensing data types are still largely or exclusively in the research phase of development and might currently be beyond the capabilities of most researchers."
• It is "tremendously important to get accurate information to validate what the remote-sensing data products appear to be telling the user. Such 'ground-truth' information might come from researchers in the field, ground-based sensors, or even higher resolution remote-sensing sources (e.g. aerial photography). [Therefore] remote-sensing products should not be taken at face value."
• "Atmospheric phenomena, mechanical problems with the sensor and numerous other effects might be distorting one's view."
• "Ecological models have a vital role in the process of converting remote-sensing data products into actual knowledge of species distributions and richness."

Despite the challenges, the authors note that remote sensing applications show great promise and more researchers are using such products every year. Yet, "to make progress, ecologists, evolutionary biologists and conservation biologists must bring their data sets on species distributions, levels of species richness, areas of endemism, and so on, to the table and combine them with the global, regional and local data sets of, for example, primary productivity and climate, which have been generated by remote-sensing researchers."

Next we'll cover a paper dealing with the latitudinal species gradient, one of the largest and typically most uniform features in biogeography. Be sure and download the paper and read before the summary.