Humans have lived in Iceland for over eleven centuries. Human activity has resulted in major environmental changes, affecting natural habitat throughout Iceland. Centuries of overgrazing and deforestation certainly have had a major impact on breeding areas, and thereby on the living conditions of many bird species. The same may be said of wetland drainage and other wetland depletion over the last century. Overhunting of certain bird species has led to population crashes and even extinction, and the introduction of mink has had a devastating impact on birdlife. Two bird species no longer breed in Iceland due to human activity: the great auk (Pinguinus impennis) is extinct due to overhunting, and the water rail (Rallus aquaticus) is regionally extinct as a breeding bird in Iceland due to large-scale wetland drainage and predation from the introduced mink.
Bird populations are affected by long-term changes in environmental conditions, in Iceland as elsewhere. Reduced grazing pressure, afforestation, and climate change will have an impact on many species, but these factors affect different species in different ways. Changes that are beneficial for some species will be disastrous for others.
Large-scale wetland drainage has been the single greatest cause of habitat disruption in Iceland. The goal was to improve farming and grazing conditions, but the inevitable result was the destruction of important bird areas. Nearly 4,000 square kilometres of wetland were drained, mainly during the period 1945–1970, and the wetland hydrology of a still greater area was impacted. No consideration was given to nature conservation in the process. Afforestation will cause more major habitat changes than other planned activities in coming years. The current policy calls for a tenfold increase in forest cover in Iceland by 2100, as stated in the report Skógar á Íslandi: Stefna á 21. öld (PDF). If this target is met, forest cover in Iceland will be at least 12%. This will have a negative impact on many bird species that live in open areas, such as the European golden plover (Pluvialis apricaria) and whimbrel (Numenius phaeopus).
Documentation of Icelandic birdlife is highly fragmentary before the 1800s. Not until the mid-eighteenth century does reasonably good information exist on what species breed in Iceland. The first naturalists to document birdlife during their travels around Iceland were Eggert Ólafsson and Bjarni Pálsson (1752–1757), followed by the Faeroese naturalist Nikolaj Mohr (1780–1781). The Danish ornithologist Frederik Faber was in Iceland in 1819–1821, and he wrote extensively on Icelandic birds.
Changes in the distribution of well-established breeding birds
Major changes have occurred in the populations and distributions of many bird species over the last two centuries. One example is the northern fulmar (Fulmarus glacialis), which proliferated and spread out rapidly until just before the turn of the millennium. The distribution of the black-tailed godwit (Limosa limosa) was limited to the lowlands of South Iceland into the early twentieth century, but it now breeds in lowland areas around Iceland and even at some highland locations. Goose populations have increased significantly in numbers from around 1950. The greylag goose (Anser anser) has spread out in the lowlands and the pink-footed goose (Anser brachyrhynchus) in the highlands.
Around 50 bird species have attempted to breed in Iceland since around 1800, the point from which fairly reliable information exists on Icelandic birdlife. Fewer than 20 of these species have become established in Iceland, half of them since the mid-twentieth century. These colonisers are all European species, with the exception of the North American black tern (Chlidonias niger surinamensis). Many were common visitors or vagrants in Iceland before they began to breed here. The bird species that colonised Iceland around or somewhat before the mid-twentieth century were either increasing in numbers in Europe at the time or spread quickly around Iceland. These include the tufted duck (Aythya fuligula), black-headed gull (Chroicocephalus ridibundus), herring gull (Larus argentatus), and lesser black-backed gull (Larus fuscus). Other colonisers only succeeded in establishing a breeding population after afforestation programmes in Iceland created suitable habitat for them: the goldcrest (Regulus regulus) and common blackbird (Turdus merula). Climate warming has also facilitated colonisation for some species.