Quantifying the distribution and potential biotic interactions between deer and flora using species distribution modelling

Invasive species are ranked as one of the leading drivers of global biodiversity loss. To mitigate their impact, we must understand the future risks caused by invasive species, particularly to flora of conservation concern. Here we used species distribution modelling (SDM) to project the current and future (RCP45 and RCP85 2050) distributions of four deer species and 13 plant species of conservation concern for the island of Ireland, quantifying changes in distributions and overlap. Large areas of suitable habitat for the deer species were predicted with high accuracy across all counties, with future climate scenarios identifying an expansion in sika deer distributions and a decrease in muntjac and fallow deer distributions. Red deer declined under the moderate climate change scenario but increased under the worst-case projection. Future projections predicted the (local) extinction of six (out of 13) endangered and vulnerable plant species. An expansion in distributions was observed for four plant species; however, these areas had large overlap with the future predictions of deer, placing further pressures on these plant species. These findings suggest that targeted conservation and management measures are required to alleviate the pressures on ‘at-risk’ plant species due to grazing from native and non-native deer.