Grapevine recovery after fire and a first look at rapid damage assessment with satellite imagery

Abstract

There is increasing scientific consensus that climate change is one of the underlying causes of the prolonged dry and hot conditions that have increased the risk of extreme fire weather inmany countries around the world. In December 2019, a bushfire occurred in the Adelaide Hills, South Australia, where 25,000 hectares were burnt, and in vineyards and surrounding areas various degrees of scorching and infrastructure damage occurred. The ability to coordinate and plan recovery after a fire event relies on robust and timely data. The current practice for measuring the scale and distribution of fire damage is to walk or drive the vineyard and score individual vines based on visual observation. The process is time consuming, subjective, or semi-quantitative at best. After the December 2019 fires, it took many months to access properties and estimate the area of vineyard damaged. This study compares the rapid assessment and mapping of fire damage using high-resolution satellite imagery with more traditional ground-based measures. Correlations between ground visual fire damage assessments and postfire NDVI (-­0.347 to -0.084) and VARIgreen (-0.333 to 0.074) satellite imagery were significant but showed no correlation to a weak negative correlation. Canopy growth, vine fertility and starch concentrations were tracked in the two seasons following the fire event to assess vine recovery. Canopy health in the seasons following the fires correlated to the severity of the initial fire damage. Severely damaged vines had reduced canopy growth, were infertile or had very low fertility as well as lower starch concentrations in buds and canes during dormancy, which reduced productivity in the seasons following the bushfire event. In contrast, vines that received minor-moderate damage were able to recover within 1-2 years. Tools that rapidly and affordably capture the extent and severity of damage over large vineyard area will allow producers, government and industry bodies to manage decisions in relation to fire recovery planning, coordination and delivery, improving the efficiency and effectiveness of their response.