Mapping Foliar Nutrition Using WorldView-3 and WorldView-2 to Assess Koala Habitat Suitability

Abstract

Conservation planning and population assessment for widely-distributed, but vulnerable, arboreal folivore species demands cost-effective mapping of habitat suitability over large areas. This study tested whether multispectral data from WorldView-3 could be used to estimate and map foliar digestible nitrogen (DigN), a nutritional measure superior to total nitrogen for tannin-rich foliage for the koala (Phascolarctos cinereus). We acquired two WorldView-3 images (November 2015) and collected leaf samples from Eucalyptus woodlands in semi-arid eastern Australia. Linear regression indicated the normalized difference index using bands “Coastal” and “NIR1” best estimated DigN concentration (% dry matter, R2 = 0.70, RMSE = 0.19%). Foliar DigN concentration was mapped for multi-species Eucalyptus open woodlands across two landscapes using this index. This mapping method was tested on a WorldView-2 image (October 2012) with associated koala tracking data (August 2010 to November 2011) from a different landscape of the study region. Quantile regression showed significant positive relationship between estimated DigN and occurrence of koalas at 0.999 quantile (R2 = 0.63). This study reports the first attempt to use a multispectral satellite-derived spectral index for mapping foliar DigN at a landscape-scale (100s km2). The mapping method can potentially be incorporated in mapping and monitoring koala habitat suitability for conservation management.

The influence of spatial patterns in foraging habitat on the abundance and home range size of a vulnerable arboreal marsupial in southeast Australia

“…The ability to determine where critical favorable feeding resources are, and what their spatial configuration is, may allow retaining them fully under certain retention strategies. High-resolution data from multispectral remote sensing that allows assessing and mapping favorable feeding resources at operational scales may therefore be an important tool in arboreal folivore conservation (Wagner, 2021;Wu, Levin, Seabrook, Moore, & McAlpine, 2019;Youngentob et al, 2012;Youngentob, Yoon, Stein, Lindenmayer, & Held, 2015). Our findings suggest that current (voluntary) prescriptions that retain a minimum of 40% basal area (DELWP and ARI staff, personal communication, April and May 2021; DELWP, 2019) or single-tree retention (Ashton & Kelty, 2018;DEPI, 2014) may not suffice for permanent greater glider persistence at a stand scale, if forage trees are poorly spatially distributed (Figures 6 and 7).…”

The Application of NIRS to Determine Animal Physiological Traits for Wildlife Management and Conservation

“…In recognition of this, Windley et al [44] were able to use NIRS to determine the concentration of in vitro digestible nitrogen in scats of female common brushtail possums (Trichosurus vulpecula) and showed that these measurements were correlated with their reproductive success. Digestible nitrogen has also been measured using NIRS of vegetation from airborne and satellite sensors in addition to laboratory spectrophotometers, opening the door to relatively rapid, landscape-scale assessments of forage quality [64,107].…”

Object Oriented Classification for Mapping Mixed and Pure Forest Stands Using Very-High Resolution Imagery

“…Indeed, maps of occurrence of tree species mixtures vs. single species would allow, by a stratified sampling approach, the extraction of sufficiently large samples of mixed forest plots. Several projects and studies have been developed at European level to map the distribution of single tree species or forest type by remote sensing with acceptable classification results [13][14][15][16]. In this regard, mapping of forest habitats types dominated by one canopy species is relatively straightforward [17,18], but where forest landscape is more heterogeneous and includes mixed-species forests, the mapping procedures may become more challenging [19].…”