The human dimension of biodiversity changes on islands

Abstract

Islands are among the last regions on Earth settled and transformed by human activities, and they provide replicated model systems for analysis of how people affect ecological functions. By analyzing 27 representative fossil pollen sequences encompassing the past 5000 years from islands globally, we quantified the rates of vegetation compositional change before and after human arrival. After human arrival, rates of turnover accelerate by a median factor of 11, with faster rates on islands colonized in the past 1500 years than for those colonized earlier. This global anthropogenic acceleration in turnover suggests that islands are on trajectories of continuing change. Strategies for biodiversity conservation and ecosystem restoration must acknowledge the long duration of human impacts and the degree to which ecological changes today differ from prehuman dynamics.

Scientists’ warning – The outstanding biodiversity of islands is in peril

“…Relative to continents, islands house a disproportionate amount of the Earth’s biodiversity, yet they are especially vulnerable to anthropogenic disturbances. Oceanic islands were among the last places to be discovered and colonized by humans, yet they are some of the most severely impacted places on the planet ( Whittaker et al, 2017 , Russell and Kueffer, 2019 , Nogué et al, 2021 ). We demonstrate here that extinction rates are disproportionately high on islands and that islands collectively serve as a warning for the uncertain future for the world’s biodiversity in the Anthropocene ( Ricketts et al, 2005 , Cardillo et al, 2006 , Johnson et al, 2017 , Díaz et al, 2020 ).…”

“…Many of the oceanic archipelagos were colonized only during the last few millennia (Caribbean, Madagascar, Balearics, Canaries, remote Melanesia, and Western Polynesia), the last millennium (New Zealand, Hawaiʻi, Eastern Polynesia, and Iceland), or even just the last few centuries (Madeira, Azores, Cabo Verde, Mascarenes, Galápagos, and Tristan da Cunha). Thus, the Late Pleistocene megafaunal extinction on the continents that began with the arrival of humans in Australia and the Americas ( Stuart, 2015 ) marks a final, still ongoing Holocene episode on the oceanic islands of the world, where insular flora and fauna (such as Caribbean sloths, New Zealand moa, Malagasy elephant bird and giant lemurs, Mascarene dodo, Hawaiian moa nalo and nēnē nui (Anseriformes), Caribbean monk seal, or Steller’s sea cow, among many others) have been driven to extinction after human colonization ( Hume, 2017 , Wood et al, 2017 , Nogué et al, 2021 ).…”

“…As shown above, extinction risks from natural causes for island biota are much higher than for continental species, even in the absence of human activities. Alarmingly, the current presence of humans on islands exacerbates the threat to island genetic heritage, biota and ecosystems, making islands hotspots of the current global biodiversity crisis ( Whittaker et al, 2017 , Leigh et al, 2019 , Russell and Kueffer, 2019 , Nogué et al, 2021 ).…”

Macaronesia as a Fruitful Arena for Ecology, Evolution, and Conservation Biology

“…Such efforts are devoted to developing management strategies that can safeguard biodiversity and ecosystem services (Butchart et al, 2010). The relatively well-known history of human settlement across the islands and associated land-use transformations aids in assessing the relative impacts of environmental (pre)historical, demographic, and socioeconomic changes on current island biodiversity (see for instance: Nogué et al, 2013Nogué et al, , 2017Nogué et al, , 2021Norder et al, 2020). Alien species constitute one of the most important threats island biotas face (Russell and Kueffer, 2019).…”

The Contribution of Kurī (Polynesian Dog) to the Ecological Impacts of the Human Settlement of Aotearoa New Zealand

“…Much archaeological and palaeoecological research has focused on the direct impacts of humans (i.e., hunting, environmental modification; Anderson, 1989;Holdaway et al, 2014;Perry et al, 2014;Nogue et al, 2021) and predation by kiore -the latter based on modern ecological (Rayner et al, 2007;Ismar et al, 2014) and palaeoecological (Wilmshurst and Higham, 2004;Wilmshurst et al, 2008) studies. In contrast, the potential impacts of kurī in particular on the pre-European contact ecosystem have largely been overlooked as they are difficult to assess, despite the potential of dogs to be a major novel predator in recently colonised ecosystems (e.g., Koungoulos and Fillios, 2020;Hixon et al, 2021).…”