Use of satellite images to monitor populations of invasive alien plants
Pontederia crassipes (Pontederiaceae: EPPO A2 List) and Hydrocotyle ranunculoides (Araliaceae: EPPO A2 List) are both listed as species of (European) Union concern (Regulation 1143/2014) and should be controlled and eradicated where they occur in European member states. Remote sensing can be utilised to record land cover of invasive alien plants and monitor spatial and temporal changes in invasive plant populations. Satellite imagery has become increasingly available for use in ecological surveys and software is available to interpret and compare imagery. In Italy, the eradication of P. crassipes and H. ranunculoides may be achievable as there are only a limited number of populations of both species. However, to achieve this, precise data on the occurrence of the populations, often in a large area is required. A study was conducted in Sardinia, in the Province of Oristano where both species occur in waterways. Imagery was used from the Copernicus Sentinel-2 satellites collected monthly between 2018 and 2021 to identify populations of the two species and the health and density of the populations were inferred by measuring the normalized difference vegetation index. Remote sensing proved useful in detecting populations of the invasive plant species and seasonal differences in the sizes of populations, and locations. Constraints included the presence of clouds in the downloaded images as in some images, the areas of concern could be totally hidden by clouds.
Sources
Ghiani L, Lozano V, Brundu G, Mazzette A, Sassu A, Gambella F (2023) Monitoring Pontederia crassipes Mart. and Hydrocotyle ranunculoides L.f. invasion on a Mediterranean island using multi-temporal satellite images. Management of Biological Invasions 14(2), 221–238.