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Accepted manuscript version. Published version available at https://doi.org/10.1126/science.1226766 . Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. ; Recently accumulated evidence has documented a climate impact on the demography and dynamics of single species, yet the impact at the community level is poorly understood. Here, we show that in Svalbard in the high Arctic, extreme weather events synchronize population fluctuations across an entire community of resident vertebrate herbivores and cause lagged correlations with the secondary consumer, the arctic fox. This synchronization is mainly driven by heavy rain on snow that encapsulates the vegetation in ice and blocks winter forage availability for herbivores. Thus, indirect and bottom-up climate forcing drives the population dynamics across all overwintering vertebrates. Icing is predicted to become more frequent in the circumpolar Arctic and may therefore strongly affect terrestrial ecosystem characteristics.

To ensure economic viability over time, any efforts to meet the Millennium Development Goals need to reconcile conservation with development interventions. Particularly, in marginal and risk prone areas erosion of resilience could make production systems more susceptible to environmental risks that compromise the economic security. By longitudinal analyses of long-term data records we investigated the impacts of big push policies on Saami pastoral ecosystems in Arctic Norway. The big push was accompanied by reindeer herd accumulation and a corresponding degradation of resilience, increasing the susceptibility to herd losses to predators and adverse winters. For the last 20 years the Norwegian government has worked to halt degradation of pasture ecosystems and reduce susceptibility to environmental risks. These intended win-win policies have mainly been based on economic incentives, which have been developed together with Saami pastoralists through negotiated agreements. We argue that the continued degradation of the Saami pastoral ecosystems is a "ghost of the development past", as the big push policies have resulted in an economic security trap (EST). The gradual reduction of resilience has persisted as the ex post payments of disaster relief and predator compensation have impeded the long-term actions to reduce susceptibility to environmental risks, i.e., ex ante policies, thereby increasing dependency on elevated economic inputs to manage the risks. The transfer of liability for managing risks to the benefactor, both through ex ante and ex post policies, has further discouraged and constrained opportunities for adaptation by the pastoralists.