Facial eczema risks in New Zealand under changing climates

Description

Three shapefiles of New Zealand showing estimates of climatic suitability for Pseudopithomyces chartarum sporulation at 0.05 degree resolution under historical and future climates.

Historical results are annual from 2008 to 2021.

Future results are for each decade from 2030 to 2120 and are based on HADGEM2 using emissions scenarios RCP2.6 and RCP8.5.

Date: January 2024 Version: v2

Owner: AgResearch

Contact: Craig Phillips (AgResearch)

Link to report / paper

PHILLIPS C, JOHNSON PL, TOMASETTO F, MCRAE K, VAN DER WEERDEN T. 2023. Predicting facial eczema risks in New Zealand under changing climates. J. New Zeal. Grasslands 85: 61-71.

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Dataset attributes

Methodology

PHILLIPS C, JOHNSON PL, TOMASETTO F, MCRAE K, VAN DER WEERDEN T. 2023. Predicting facial eczema risks in New Zealand under changing climates. J. New Zeal. Grasslands 85: 61-71.

A simple model was developed to estimate climatic suitability for sporulation of Pseudopithomyces chartarum--and thereby facial eczema risk--using published descriptions of the response of P. chartarum to temperature and moisture. Suitability was calculated as the normalised product of a temperature index and a rainfall index, each with ranges 0-1. The temperature index was calculated as the overlap between the observed air temperature range at a location and the range 14 to 35 °C divided by the observed air temperature range at the location. The rainfall index increased linearly from zero when a location had 0 mm rain per day to one when it had rain in the range of 0.7 to 5 mm per day, and then declined linearly from one to zero through the range 5 to 7 mm per day, then remained zero with rain greater than 7 mm per day. Data for daily rainfall and daily minimum and maximum air temperature were from NIWA’s Virtual Climate Station Network, had a spatial resolution of 0.05 degrees, and were converted to weekly means for use in the modelling.

Model estimates of climatic suitability for P. chartarum sporulation were compared to counts of P. chartarum spores in pasture that had been curated by Gribbles Veterinary from 2008 to 2021. The counts had been aggregated to districts and postcodes and this coarse spatial resolution made comprehensive validation of the model impossible. However, the aggregated spore counts were used to calculate for each district or postcode an annual index of potential exposure to facial eczema. Exposure was the product of the annual mean spore count (i.e., level of exposure), the proportion of annual spore counts >30000 (i.e., duration of exposure), and the annual number of districts or postcodes with spore counts >30000 (i.e., spatial extent of exposure). Annual correlations between estimated climatic suitability and exposure were tested by linear regression and were significantly positive. Model results also accorded with qualitative descriptions of annual variation in facial eczema severity in New Zealand.

The model was used to estimate the potential climatic suitability of New Zealand for P. chartarum sporulation under future climate scenarios (Mullan, Sood, and Stuart 2018) predicted by the HADGEM2 global circulation model under Representative Concentration Pathways (RCP) 2.6 (optimistic) and 8.5 (pessimistic)

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