The potential of small-Unmanned Aircraft Systems for the rapid detection of threatened unimproved grassland communities using an Enhanced Normalized Difference Vegetation Index

Abstract

The loss of unimproved grassland has led to species decline in a wide range of taxonomic groups. Agricultural intensification has resulted in fragmented patches of remnant grassland habitat both across Europe and internationally. The monitoring of remnant patches of this habitat is critically important, however, traditional surveying of large, remote landscapes is a notoriously costly and difficult task. The emergence of small-Unmanned Aircraft Systems (sUAS) equipped with low-cost multi-spectral cameras offer an alternative to traditional grassland survey methods, and have the potential to progress and innovate the monitoring and future conservation of this habitat globally. The aim of this article is to investigate the potential of sUAS for rapid detection of threatened unimproved grassland and to test the use of an Enhanced Normalized Difference Vegetation Index (ENDVI). A sUAS aerial survey is undertaken at a site nationally recognised as an important location for fragmented unimproved mesotrophic grassland, within the south east of England, UK. A multispectral camera is used to capture imagery in the visible and near-infrared spectrums, and the ENDVI calculated and its discrimination performance compared to a range of more traditional vegetation indices. In order to validate the results of analysis, ground quadrat surveys were carried out to determine the grassland communities present. Quadrat surveys identified three community types within the site; unimproved grassland, improved grassland and rush pasture. All six vegetation indices tested were able to distinguish between the broad habitat types of grassland and rush pasture; whilst only three could differentiate vegetation at a community level. The Enhanced Normalized Difference Vegetation Index (ENDVI) was the most effective index when differentiating grasslands at the community level. The mechanisms behind the improved performance of the ENDVI are discussed and recommendations are made for areas of future research and study.

The use of small-Unmanned Aerial Systems for high resolution analysis for intertidal wetland restoration schemes

“…Furthermore, the application of sUAS surveying may also be applicable to help understand vegetation development and ecosystem functioning in relation to a site's morphological development through vegetation and habitat mapping, as previously performed in other settings elsewhere (e.g. Belluco et al, 2006;Strong et al, 2017). This potential application, including multi-spectral vegetation analysis, should form the basis of future research focussed on the value and use of sUAS in intertidal settings.…”

Fine scale plant community assessment in coastal meadows using UAV based multispectral data

“…With the advent and rapid development of GIS software and the large amount of remotely sensed data available, these tools have been increasingly used for predictive plant community mapping (Burnside & Waite, 2011). Among the wide range of remote sensing techniques and platforms, there are many studies that use passive multispectral remotely sensed data to identify plant communities (Townsend & Walsh, 2001;Brown et al, 2006;Balzarolo et al, 2009;Berni et al, 2009;Hamada et al, 2011;Strong et al, 2017). These studies used a methodology based on identifying specific reflectance values in different wavelengths of distinct vegetation by performing some form of classification, either unsupervised or supervised (Jones & Vaughn, 2010).…”

“…Despite its great potential and recent progress, the use of UAVs and classification algorithms for mapping grassland plant communities has received little attention in the scientific literature. Some studies have utilized different sensors and statistical algorithms to automatically map grassland communities, from consumer grade cameras (Gonçalves et al, 2015; Lu & He, 2017) to multispectral sensors (Strong et al, 2017). In addition, UAVs have been used to estimate aboveground biomass production in grasslands (Wang et al, 2017).…”

The evolution of embryonic creek systems in a recently inundated large open coast managed realignment site

“…sUAS are being used increasingly across a number of scientific disciplines as an alternative approach to provide high-resolution detailed imagery (e.g., James and Robson 2014;Tonkin and Midgley 2016;Strong et al 2017). Images can be used for rapid reconstruction of surface geometry, providing there is sufficient overlap between images, without the need for camera position or orientation data through automated photogrammetric techniques (e.g., James and Robson 2012;Westoby et al 2012;Javemick et al 2014;Nolan et al 2015).…”