Climate change in Europe. 1. Impact on terrestrial ecosystems and biodiversity. A review

Ecosystems have an essential role in providing services to humankind such as nutrient cycling, pest control, pollination, quality of life, and hydrological, atmospheric and climatic regulation. About 60% of the world’s known ecosystems are currently used unsustainably. In Europe, the richness and abundance of biodiversity is undergoing significant decline, partly due to climate change. This article outlines the impacts of climate change on biodiversity by showing both observed and projected changes in the distribution and phenology of plants and animals (phenology refers to changes in the timing of seasonal events). The four major findings are the following. (1) Concerning the distribution of plant species, climate change is responsible for the observed northward and uphill distribution shifts of many European plant species. By the late 21st century, distributions of European plant species are projected to have shifted several hundred kilometres to the north, forests are likely to have contracted in the south and expanded in the north, and 60% of mountain plant species may face extinction. The rate of change will exceed the ability of many species to adapt. (2) Concerning plant phenology, the timing of seasonal events in plants is changing across Europe due to changes in climate conditions. For instance, 78% of leaf unfolding and flowering records show advancing trends. Between 1971 and 2000, the average advance of spring and summer was 2.5 days per decade. The pollen season starts on average 10 days earlier and is longer than 50 years ago. Trends in seasonal events will continue to advance as climate warming increases in the years and decades to come. (3) Concerning the distribution of animal species, Europe’s birds, insects, and mammals are moving northwards and uphill in response to observed climate change. Rate of climate change, habitat fragmentation and other obstacles will impede the movement of many animal species. Distribution changes are projected to continue. Suitable climatic conditions for Europe’s breeding birds are projected to shift nearly 550 km northeast by the end of the century. Projections for 120 native European mammals suggest that up to 9% face extinction during the 21st century. (4) Concerning animal phenology, climatic warming has caused advancement in the life cycles of many animal groups, including frogs spawning, birds nesting and the arrival of migrant birds and butterflies. Seasonal advancement is particularly strong and rapid in the Arctic. Breeding seasons are lengthening, allowing extra generations of temperature-sensitive insects such as butterflies, dragonflies and pest species to be produced during the year. These trends are projected to continue as climate warming increases in the decades to come. Populations may explode if the young are not exposed to normal predation pressures. Conversely, populations may crash if the emergence of vulnerable young is not in synchrony with their main food source or if shorter hibernation times lead to declines in body condition.