By R.M.M. Crawford
The Arctic is changing. How it will change is uncertain. In contemplating the future in the far north a distinction has to be made between the maritime and the terrestrial Arctic. The Arctic Ocean is a relatively monotonous region, whether it be frozen or unfrozen. By contrast, the terrestrial Arctic, the Tundra and Taiga, are ecologically diverse with habitats ranging from polar mountains and deserts to frozen expanses of Tundra, giving way in the south to the bogs and forests of the Taiga. All life in polar regions has to contend with similar problems irrespective of whether it is plant, animal, or human. Therefore it is possible to attempt to provide a circumpolar perspective of evolution and adaptation in a region with short growing seasons and variable temperature conditions.
Whatever fate may eventually overtake the polar bears in the Arctic Ocean, it is inevitable that the melting of the oceanic ice will make a fundamental difference to their way of life. However, the outlook for most inhabitants of the terrestrial environments of the Arctic is entirely different. Until very recently, the sun was already declining in the sky before the snow and ice had retreated from its winter expanse. With climatic warming, spring is now coming earlier and the arctic lands are capturing significantly more energy. Plants begin to grow sooner, flowering takes place earlier, and the length of the growing season is extending. Already, results from a two-decade summer warming experiment in an Alaskan Tundra ecosystem have shown that warming has increased plant biomass and woody plant dominance. If these changes continue, these northern lands will provide more copious forage for lemmings, voles, and geese as well as improving grazing for the larger herbivores such as muskoxen and reindeer.
In the more southern parts of the Arctic, human disturbance and increasing parasite infections may cause problems. Nevertheless, this can be counteracted by northerly migrations. If suitably encouraged, reindeer might even recolonize Franz Josef Land and muskoxen should become more numerous. An improvement in forage will benefit to herbivores. Which in turn could provide more prey for wolves, foxes, and raptors. The brown bears of the taiga will have a greater supply of berries and other forage which may eventually enable them to move further north, where they may begin to hybridize and possibly have an effect in increasing bear diversity. By interbreeding with brown bears the polar bears may recover some of their ancestral characteristics, and perhaps even the dentition needed to vary their present entirely carnivorous diet.
The terrestrial Arctic has undergone many changes in the past. One common feature for the plants, animals, and human populations of the Arctic that will remain despite climatic warming is the capacity to survive the long polar winter. Sufficiency of energy reserves for this long adverse season is fundamental to survial during the polar night This is common to plants and animals, just as it has demanded foresight and planning for human settlers. This facet of arctic life has left an imprint on the evolution of the present-day flora and fauna, with a biota that has specialized in adapting to a range of very different habitats. Just how these different Tundra and Taiga habitats will respond ecologically to change will depend in large measure on the adaptive ability of the inhabitants — plant, animal, and human — in terms of physiology, reproduction, migration, and dormancy. The dangers of disturbance and pollution must also be considered in context.
Recent advances in genetics and molecular biology are providing a new assessment of the evolutionary and ecological history of the plants, animals, as well as the human inhabitants in this region. In past climatic history, an ice-free Arctic Ocean has been the norm, and should this condition return it will not destroy the terrestrial Arctic. As long as the Earth rotates with approximately its present angle to the ecliptic, the polar night will persist and preserve the uniqueness of the polar scene. If such views seem too optimistic and resemble “a first blast of the trumpet against the monstrous regiment of arctic pessimists” (cf John Knox, 1558), they should be read as just one possible outcome of climatic warming in relation to the terrestrial Arctic.
Robert Crawford is Emeritus Professor of Biology of the University of St Andrews. He is the author of Tundra-Taiga Biology. He was awarded a DSc (Liège) in 1960, and made a Fellow of the Royal Society of Edinburgh in 1973. He is a Fellow of the Linnaean Society (1999) and Associate Member of the Belgian Royal Academy (2001).