Understanding the Age of Extinction
We are living through a biodiversity crisis, or what scientists are calling the ‘sixth mass extinction’, as around 1 million species face extinction, many within decades.
May 7th 2021
With many species experiencing population declines and range contractions worldwide, it is reassuring that new technologies are aiding conservation efforts. One fascinating area is the field of remote sensing, which for the scope of this article, is a method of obtaining information about the environment by recording, measuring, and interpreting imagery and data derived from aircraft or satellite based sensors. There are two types of sensors used in remote sensing: passive sensors, and active sensors.
Passive sensors detect energy that was either reflected by the feature as visible light, or was absorbed the feature and then was re-emitted as thermal infrared wavelengths. Many passive remote sensing systems include multiple components which each detect a portion of the electromagnetic spectrum (each called “bands”).
LANDSAT, a series of satellites fitted with such multispectral scanners, have been pivotal in the development of geosciences. The latest version, LANDSAT 8, was launched in February, 2013, features two sensors: one that detects eight bands across the visible and short wave infrared spectral regions, and another that detects two long wave infrared bands.
The data collected by these passive sensors can be manipulated to derive many different types of information, including true-color images, vegetation coverage, soil moisture content, and water depth. In active sensors, the sensor itself emits radiation, which then moves toward the targeted object, is then reflected back towards the sensor, and recorded. Familiar examples of active sensors are RADAR and SONAR. A newer and less renowned type of active sensor is LiDAR.
LiDAR, which stands for Light Detection and Ranging, is a fascinating active remote sensing technology that employs pulsed laser beams to measure distances from sensor to target. The underlying principal of LiDAR is simple: light is directed at a target, and the time that it takes to bounce back at a sensor is measured to determine the distance between the sensor and target. The trick is the instrument fires extremely rapidly (some up to 150,000 pulses per second), which paired with an extremely sensitive sensor, allows for the creation of complex fine-resolution 3-D models of the Earth’s surface.
I’ve glossed over many of the technical aspects of collecting and processing remotely sensed data (mostly because I’m no expert!). However, the important thing to know is that while many of these technologies are not new, their use and application in the fields of ecology and conservation are expanding rapidly. As of 2014, there is even a journal (Remote Sensing in Ecology and Evolution) devoted to this field alone.
So what are the uses of remote sensing in conservation? Here are a few general applications as discussed in a 2014 paper published in Conservation Biology:
While there are many specific examples of the application of remote sensing in animal conservation, one of the most impressive and successful was a project that created a habitat suitability model for each of the four chimpanzee subspecies across their entire range. The model was informed by several variables derived from LANDSAT data. One of the greatest threats to chimpanzees is habitat loss, mainly from deforestation, so this information was a great asset to direct conservation efforts to help preserve the species.
Another interesting study, published in 2017, was conducted in Germany, where limited field data regarding the known occurrence of an invasive plant species was used in conjunction with airborne images from a novel “hyperspectral” spectrometer (it is called that because it records spectral data in 285 bands, compared to LANDSAT 8’s 10 bands) to create a predictive distribution map for the species. While the species is reportedly small and inconspicuous, this predicted distribution was found to be 75% accurate. This study shows how remote sensing can improve the efficiency of conservation efforts, like in the ever-waging battle against invasive species.
While the prior two examples passive sensors were used, LiDAR is also a promising tool for conservation. Because the technology allows the creation of 3-D models, it can be used to study habitat structure, rather than composition, across large spatial scales. A 2009 paper in Forest Ecology and Management used LiDAR to study the habitat of capercaillie (a large, angry grouse species) across a forest reserve. The predictive model incorporating LiDAR-derived habitat structure information (eg. tree canopy cover), showing that this technology can aid in delineating the species habitat.
Remote sensing is an immense and fascinating field. These technologies will be essential to successful conservation efforts in the 21st century. If you are interested in the topic, there is a plethora of information to wade through – maybe even a career in geosciences would be right for you!
By WorkingAbroad Blog Writer Sean Feagan
All images from Wikimedia Commons