Remote Sensing in Ecology: Satellites, Drones, and the View from Above

Remote sensing — the acquisition of information about Earth's surface from airborne or spaceborne platforms without direct physical contact — has become one of the most important tools in conservation science. Satellite imagery now enables continuous monitoring of forest cover, grassland condition, wetland extent, and coastal habitat quality at global scale with spatial resolution that has improved from kilometres to metres over the past three decades. Drone-based surveys allow detailed mapping of habitats, counting of wildlife populations, and detection of individual plants or animals at scales and resolutions that are impractical with satellite imagery. The combination of satellite monitoring, drone surveys, machine learning image classification, and cloud computing platforms has given conservation biologists a landscape-scale observational capability that was unimaginable twenty years ago.

Deforestation Monitoring

The most impactful application of satellite remote sensing in conservation is deforestation monitoring — the use of satellite imagery to detect and quantify forest loss with near-real-time frequency across entire countries or continents. The Global Forest Watch platform (World Resources Institute) uses a combination of Landsat, MODIS, and VIIRS satellite data to generate weekly deforestation alerts at 30-metre resolution across the tropics — enabling conservation organisations, governments, and journalists to identify illegal clearance events within days of their occurrence. This near-real-time monitoring capability has fundamentally changed the capacity of authorities to respond to illegal deforestation: events that would previously have gone undetected for months can now trigger field verification within a week of satellite detection.

Counting Animals from Above

The use of drones equipped with high-resolution cameras and thermal imaging sensors to survey wildlife populations is one of the most rapidly growing applications of remote sensing in conservation. Traditional aerial surveys of large mammals — conducted from fixed-wing aircraft or helicopters — required skilled human observers who could detect and count animals in real time from a moving platform, with the associated fatigue, observer variability, and detection bias that human observers inevitably introduce. Drone surveys, combined with computer vision algorithms that automatically detect and classify animals in aerial imagery, offer higher detection rates, more consistent methodology, and dramatically lower costs per survey area. Studies comparing drone surveys to traditional aerial counts have consistently shown higher detection rates in drone surveys — by factors of 2-5 for some species — particularly for animals in dense vegetation or difficult terrain.

LiDAR — Mapping Forest Structure from Above

LiDAR (Light Detection and Ranging) — a remote sensing technology that emits laser pulses and measures the time of return from different surfaces — has transformed the ability to characterise three-dimensional forest structure at landscape to continental scales. Unlike passive optical sensors that measure only the canopy surface visible from above, LiDAR pulses penetrate the forest canopy through gaps, returning signals from multiple height levels — the top of the canopy, intermediate branch levels, the understorey, and the ground surface — and allowing reconstruction of the complete vertical forest profile from a single overflying pass. From this data, researchers can calculate canopy height, canopy cover, basal area, above-ground biomass, and structural complexity metrics (such as the coefficient of variation of canopy height, which correlates with habitat quality for many forest-dependent species) across entire landscapes. Global LiDAR datasets — now available from the ICESat-2 satellite and the GEDI instrument aboard the International Space Station — are providing the first globally consistent measurements of forest height and biomass needed to close major uncertainties in the global carbon budget and to monitor forest degradation as well as deforestation in protected and managed areas.

Satellite Tracking — Following Animals Across the Globe

The miniaturisation of GPS and Argos satellite tracking technology has enabled wildlife telemetry at spatial and temporal scales that were unimaginable a generation ago. Tags weighing less than 1 gram can now be attached to songbirds, attaching for multi-year deployments that track individual movement through entire annual cycles from breeding grounds in the Arctic to wintering areas in tropical Africa or South America. The Movebank database — a global repository of animal tracking data maintained by the Max Planck Institute of Animal Behavior — contains movement data for over 1,000 species and 1.5 billion location records, representing the largest compilation of animal movement data ever assembled. Analysis of these data has revealed migration routes, wintering areas, and critical stopover sites for hundreds of species, informing conservation planning at continental scales. The Global Flyway Network — which coordinates conservation across the migration routes of shorebirds from Siberia and Alaska through East Asia to Australia and New Zealand — is built on satellite tracking data that first revealed the routes, stopover sites, and timing of these extraordinary journeys.