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Loe LE, Liston GE, Pigeon G, Barker K, Horvitz N, Stien A, Forchhammer M, Getz WM, Irvine RJ, Lee A, Movik LK, Mysterud A, Pedersen ÅØ, Reinking AK, Ropstad E, Trondrud LM, Tveraa T, Veiberg V, Hansen BB, Albon SD. The neglected season: Warmer autumns counteract harsher winters and promote population growth in Arctic reindeer. Glob Chang Biol 2020; 27:993-1002. [PMID: 33231361 DOI: 10.1111/gcb.15458] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 10/21/2020] [Indexed: 06/11/2023]
Abstract
Arctic ungulates are experiencing the most rapid climate warming on Earth. While concerns have been raised that more frequent icing events may cause die-offs, and earlier springs may generate a trophic mismatch in phenology, the effects of warming autumns have been largely neglected. We used 25 years of individual-based data from a growing population of wild Svalbard reindeer, to test how warmer autumns enhance population growth. Delayed plant senescence had no effect, but a six-week delay in snow-onset (the observed data range) was estimated to increase late winter body mass by 10%. Because average late winter body mass explains 90% of the variation in population growth rates, such a delay in winter-onset would enable a population growth of r = 0.20, sufficient to counteract all but the most extreme icing events. This study provides novel mechanistic insights into the consequences of climate change for Arctic herbivores, highlighting the positive impact of warming autumns on population viability, offsetting the impacts of harsher winters. Thus, the future for Arctic herbivores facing climate change may be brighter than the prevailing view.
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Affiliation(s)
- Leif Egil Loe
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Aas, Norway
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, CA, USA
| | - Glen E Liston
- Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, CO, USA
| | - Gabriel Pigeon
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Aas, Norway
| | - Kristin Barker
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, CA, USA
| | - Nir Horvitz
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, CA, USA
| | - Audun Stien
- Department of Arctic and Marine Biology, The Arctic University of Norway, Tromsø, Norway
| | | | - Wayne Marcus Getz
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, CA, USA
- School of Mathematical Sciences, University of KwaZulu-Natal, Durban, South Africa
| | - Robert Justin Irvine
- Frankfurt Zoological Society, Addis Ababa, Ethiopia
- The James Hutton Institute, Aberdeen, UK
| | - Aline Lee
- Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway
| | - Lars K Movik
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Aas, Norway
| | - Atle Mysterud
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Blindern, Oslo, Norway
| | | | - Adele K Reinking
- Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, CO, USA
| | - Erik Ropstad
- Faculty of Veterinary Science, Norwegian University of Life Sciences, Oslo, Norway
| | - Liv Monica Trondrud
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Aas, Norway
| | - Torkild Tveraa
- Department of Arctic and Marine Biology, The Arctic University of Norway, Tromsø, Norway
| | | | - Brage B Hansen
- Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway
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Zamin TJ, Côté SD, Tremblay JP, Grogan P. Experimental warming alters migratory caribou forage quality. Ecol Appl 2017; 27:2061-2073. [PMID: 28653471 DOI: 10.1002/eap.1590] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 04/19/2017] [Indexed: 06/07/2023]
Abstract
Global declines in caribou and reindeer (Rangifer) populations have drawn attention to the myriad of stressors that these Arctic and boreal forest herbivores currently face. Arctic warming has resulted in increased tundra shrub growth and therefore Rangifer forage quantity. However, its effects on forage quality have not yet been addressed although they may be critical to Rangifer body condition and fecundity. We investigated the impact of 8 yrs of summer warming on the quality of forage available to the Bathurst caribou herd using experimental greenhouses (n = 5) located in mesic birch hummock tundra in the central Canadian Low Arctic. Leaf forage quality and digestibility characteristics associated with nutrients (nitrogen and phosphorus), phenolics, and fiber were measured on the deciduous shrub Betula glandulosa (an important Rangifer diet component) at six time points through the growing season, and on five other very common vascular plant and lichen species in late summer. Experimental warming reduced B. glandulosa leaf nitrogen concentrations by ~10% in both late June and mid-July, but not afterwards. It also reduced late summer forage quality of the graminoid Eriophorum vaginatum by increasing phenolic concentrations 38%. Warming had mixed effects on forage quality of the lichen Cetraria cucullata in that it increased nutrient concentrations and tended to decrease fiber contents, but it also increased phenolics. Altogether, these warming-induced changes in forage quality over the growing season, and response differences among species, highlight the importance of Rangifer adaptability in diet selection. Furthermore, the early season reduction in B. glandulosa nitrogen content is a particular concern given the importance of this time for calf growth. Overall, our demonstration of the potential for significant warming impacts on forage quality at critical times for these animals underscores the importance of effective Rangifer range conservation to ensure sufficient appropriate habitat to support adaptability in forage selection in a rapidly changing environment.
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Affiliation(s)
- Tara J Zamin
- Department of Biology, Queen's University, Kingston, Ontario, K7L 3N6, Canada
- School of Biological Sciences, Monash University, Clayton, Victoria, 3800, Australia
| | - Steeve D Côté
- Caribou Ungava, Département de Biologie, and Centre d'études Nordiques, Université Laval, Québec, Quebec, G1V 0A6, Canada
| | - Jean-Pierre Tremblay
- Caribou Ungava, Département de Biologie, and Centre d'études Nordiques, Université Laval, Québec, Quebec, G1V 0A6, Canada
| | - Paul Grogan
- Department of Biology, Queen's University, Kingston, Ontario, K7L 3N6, Canada
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Albon SD, Irvine RJ, Halvorsen O, Langvatn R, Loe LE, Ropstad E, Veiberg V, van der Wal R, Bjørkvoll EM, Duff EI, Hansen BB, Lee AM, Tveraa T, Stien A. Contrasting effects of summer and winter warming on body mass explain population dynamics in a food-limited Arctic herbivore. Glob Chang Biol 2017; 23:1374-1389. [PMID: 27426229 DOI: 10.1111/gcb.13435] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 07/05/2016] [Indexed: 05/27/2023]
Abstract
The cumulative effects of climate warming on herbivore vital rates and population dynamics are hard to predict, given that the expected effects differ between seasons. In the Arctic, warmer summers enhance plant growth which should lead to heavier and more fertile individuals in the autumn. Conversely, warm spells in winter with rainfall (rain-on-snow) can cause 'icing', restricting access to forage, resulting in starvation, lower survival and fecundity. As body condition is a 'barometer' of energy demands relative to energy intake, we explored the causes and consequences of variation in body mass of wild female Svalbard reindeer (Rangifer tarandus platyrhynchus) from 1994 to 2015, a period of marked climate warming. Late winter (April) body mass explained 88% of the between-year variation in population growth rate, because it strongly influenced reproductive loss, and hence subsequent fecundity (92%), as well as survival (94%) and recruitment (93%). Autumn (October) body mass affected ovulation rates but did not affect fecundity. April body mass showed no long-term trend (coefficient of variation, CV = 8.8%) and was higher following warm autumn (October) weather, reflecting delays in winter onset, but most strongly, and negatively, related to 'rain-on-snow' events. October body mass (CV = 2.5%) increased over the study due to higher plant productivity in the increasingly warm summers. Density-dependent mass change suggested competition for resources in both winter and summer but was less pronounced in recent years, despite an increasing population size. While continued climate warming is expected to increase the carrying capacity of the high Arctic tundra, it is also likely to cause more frequent icing events. Our analyses suggest that these contrasting effects may cause larger seasonal fluctuations in body mass and vital rates. Overall our findings provide an important 'missing' mechanistic link in the current understanding of the population biology of a keystone species in a rapidly warming Arctic.
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Affiliation(s)
| | | | - Odd Halvorsen
- Natural History Museum, University of Oslo, Box 1172 Blindern, NO-0318, Oslo, Norway
| | - Rolf Langvatn
- University Courses in Svalbard (UNIS), P.O. Box 156, NO-9171, Longyearbyen, Norway
- Norwegian Institute for Nature Research (NINA), P.O. Box 5685 Sluppen, NO-7485, Trondheim, Norway
| | - Leif E Loe
- Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432, Aas, Norway
| | - Erik Ropstad
- Norwegian University of Life Sciences, P.O. Box 8146, NO-0033, Oslo, Norway
| | - Vebjørn Veiberg
- Norwegian Institute for Nature Research (NINA), P.O. Box 5685 Sluppen, NO-7485, Trondheim, Norway
| | - René van der Wal
- Aberdeen Centre for Environmental Sustainability (ACES), School of Biological Sciences, University of Aberdeen, Aberdeen, AB24 3UU, UK
| | - Eirin M Bjørkvoll
- Centre for Biodiversity Dynamics (CBD), Department of Biology, Norwegian University of Science & Technology (NTNU), N-7491, Trondheim, Norway
| | - Elizabeth I Duff
- Biomathematics & Statistics Scotland (BioSS), Aberdeen, AB15 8QH, UK
| | - Brage B Hansen
- Centre for Biodiversity Dynamics (CBD), Department of Biology, Norwegian University of Science & Technology (NTNU), N-7491, Trondheim, Norway
| | - Aline M Lee
- Centre for Biodiversity Dynamics (CBD), Department of Biology, Norwegian University of Science & Technology (NTNU), N-7491, Trondheim, Norway
| | - Torkild Tveraa
- Norwegian Institute for Nature Research (NINA), Fram Centre, NO-9296, Tromsø, Norway
| | - Audun Stien
- Norwegian Institute for Nature Research (NINA), Fram Centre, NO-9296, Tromsø, Norway
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