Human-mediated introduction of geoengineering earthworms in the Fennoscandian arctic

Abstract

It is now well established that European earthworms are re-shaping formerly glaciated forests in North America with dramatic ecological consequences. However, few have considered the potential invasiveness of this species assemblage in the European arctic. Here we argue that some earthworm species (Lumbricus rubellus, Lumbricus terrestris and Aporrectodea sp.) with great geomorphological impact (geoengineering species) are non-native and invasive in the Fennoscandian arctic birch forests, where they have been introduced by agrarian settlers and most recently through recreational fishing and gardening. Our exploratory surveys indicate no obvious historical dispersal mechanism that can explain early arrival of these earthworms into the Fennoscandian arctic: that is, these species do not appear to establish naturally along coastlines mimicking conditions following deglaciation in Fennoscandia, nor were they spread by early native (Sami) cultures. The importance of anthropogenic sources and the invasive characteristics of L. rubellus and Aporrectodea sp. in the arctic is evident from their radiation outwards from abandoned farms and modern cabin lawns into adjacent arctic birch forests. They appear to outcompete previously established litter-dwelling earthworm species (i.e. Dendrobaena octaedra) that likely colonized the Fennoscandian landscape rapidly following deglaciation via hydrochory and/or dispersal by early Sami settlements. The high geoengineering earthworm biomasses, their recognized ecological impact in other formerly glaciated environments, and their persistence once established leads us to suggest that geoengineering earthworms may pose a potent threat to some of the most remote and protected arctic environments in northern Europe.

Invasive earthworms unlock arctic plant nitrogen limitation

“…which, once introduced by humans, can establish in the Arctic (Fig. 1) and reshape the arctic soil morphology in our study region in northern Sweden 27 . We use an arctic common garden experiment conducted over two growing seasons ( Supplementary Fig.…”

“…have been found (utilizing the mineral soil as a habitat) in the arctic biome (purple shading) divided into three major geographical zones (sub-, low-, and high-arctic). Sites are compiled from previously published studies 27,47,49,[52][53][54][55] and findings presented in the Global Biodiversity Information Facility database. Red rectangle indicates a reported finding of L. rubellus in Greenland where the specific site was not reported 56 .…”

Side‐swiped: ecological cascades emanating from earthworm invasions

“…Of particular concern is that four of the six ecological cascades within the broader cascade complex described earlier (Figure 4) negatively affect forest productivity and diversity, and that earthworms are likely to exacerbate increasing drought effects caused by a warming climate; those effects will likely have dramatic impacts on whether climate warming increases or decreases forest productivity (Reich et al 2018). These effects of earthworm invasion can occur throughout temperate and boreal forest biomes, and although most studies cover North America, similar earthworm invasion effects have taken place near the northern edge of the boreal forest in Europe (Wackett et al 2017).…”

“…These effects of earthworm invasion can occur throughout temperate and boreal forest biomes, and although most studies cover North America, similar earthworm invasion effects have taken place near the northern edge of the boreal forest in Europe (Wackett et al . ).…”

Invasive lumbricid earthworms in North America—Different life histories but common dispersal?

“…In general, earthworms are susceptible to prolonged freezing periods, drought and geographic barriers like mountain ranges and large water bodies, which usually restrict their natural dispersal pattern (Eggleton, Inward, Smith, Jones, & Sherlock, 2009;Reynolds, 1994). However, they recently were recorded from interior Alaska and Fennoscandia suggesting that they can also withstand very low temperatures (Booysen, Sikes, Bowser, & Andrews, 2018;Wackett, Yoo, Olofsson, & Klaminder, 2018). Active dispersal of earthworms is slow, but they were able to spread across northern North America within a few hundred years by passive dispersal or repeated introductions, and today they are present in large areas from the east coast to the Midwest, east of the Rocky Mountains in Canada, and the Pacific coast (Hale et al, 2005;Holdsworth, Frelich, & Reich, 2007;Reynolds, 1977Reynolds, , 1994Reynolds, , 2016Reynolds, Linden, & Hale, 2002;Scheu & Parkinson, 1994).…”