Modelling harvest of Greenland barnacle geese and its implications in mitigating human–wildlife conflict

Abstract

Arctic-breeding goose populations have increased in recent decades and their expansion into agricultural areas has caused increasing conflict with farmers due to the damage they cause. Lethal control and scaring are common management strategies of conflict mitigation. Management typically focuses on local/national scales, making addressing the impact of localised control on the wider population challenging, particularly when populations move over large areas and cross international borders. We construct an integrated population model (IPM) to assess the cumulative impact of all shooting harvest (hunting and derogation shooting) on the Greenland barnacle goose, Branta leucopsis. We use data from monitoring schemes throughout the migratory flyway and use population projections to evaluate the impact of potential future shooting strategies on abundance. Our model suggests flyway abundance has declined since its 2012 peak, consistent with an increase in harvest rate and low productivity. Harvest rate increase was most pronounced on Islay (rising from 2% to 7% from 2011 to 2017), suggesting this was a probable cause of flyway abundance decline. Islay abundance has declined since derogation shooting began in 2000, while abundance at other wintering sites has increased. This may indicate that declines in Islay abundance may be due to both shooting mortality and emigration from Islay. Should future flyway-level harvest rates increase, further declines in abundance could be expected, and are likely to be more pronounced if harvests are extended to the entire winter range. Conversely, should harvest rates decline, an increase in abundance is predicted. Projections can therefore be used to allocate flyway-level harvest rates to alleviate local pressure without hindering flyway-level management objectives. Synthesis and applications. Our findings demonstrate the impact of local harvests on global abundance, emphasising the importance of internationally coordinated monitoring and management strategies of migratory species. IPMs provide a framework for adaptation to incorporate additional data when they become available and enable comparisons of future harvest scenarios to inform management strategies throughout the flyway.