Human impact and ecological changes during prehistoric settlement on the Canary Islands

Abstract

Oceanic islands remained free of humans until relatively recent times. On contact, humans encountered pristine environments with unique ecosystems and species highly vulnerable to novel impacts. In the course of rendering an island habitable, the new settlers transformed it through fire, deforestation, hunting and introduction of pests and weeds. The result, as described for many oceanic islands globally, has been a catastrophe for biodiversity. Here we present the case of the Canary Islands, an Atlantic archipelago renowned for its exceptional biodiversity, and show that these islands have been no exception to the general rule. We review the archaeological, palaeoecological, palaeontological and ecological literature for the archipelago and discuss the ecological consequences e in particular habitat transformation and biodiversity loss e of human settlement. In contrast to previous views that prehistoric humans had only limited impacts on these islands, we show that vegetation change, increased fire, soil erosion, species introductions and extinctions follow the familiar oceanic pattern. Timing of human settlement of the Canary Islands has been controversial, with revised archaeological dates suggesting a relatively late arrival at the beginning of the Common Era, while palaeoecological and palaeontological evidence favours a presence several centuries earlier. While the matter is still not settled, we suggest that settlement sometime between 2400 and 2000 cal years BP is a possibility.

Evolutionary winners are ecological losers among oceanic island plants

“…To test whether species belonging to diversified or nondiversified lineages play an important role in structuring the selected communities in which they participate we applied a bootstrap approach (Crawley, 2007). We tested if the mean proportion of the relative cover of species belonging to diversified lineages in each MET on a certain island was significantly different from its proportion in the island's species pool, that is, if they are under-or overrepresented in the local community.…”

“…To test for linear relationships between the proportion of relative cover of diversified species in community plots and plot elevation, slope and community tree cover, we applied generalized linear mixed models (GLMM) with a binomial error distribution, as recommended for continuous proportional data (Crawley, 2007).…”

“…We use a modified Raunkiaer (1934) classification: trees (micro-, meso-and macrophanerophytes, height >4 m), shrubs (nanophanerophytes height: 0.25-4 m), dwarf shrubs (chamaephytes, which are mostly woody on the Canary Islands, height: <0.25 m), perennial herbs with bulbs or rhizomes (geophytes), perennial herbs (hemicryptophytes), annual herbs (therophytes). The last row percentages refer to the prevalence of both groups within the entire Canarian flora and intensifying after Castilian settlement in the 15th century (de Nascimento et al, 2020).…”

Anthropogenic transitions from forested to human-dominated landscapes in southern Macaronesia

“…2,000 cal BP (14) and subsequently conquered by the Castilians over the course of the 15th century. In the early colonial period, both archipelagos were inextricably connected to the development and spread of agricultural, economic, and societal practices in the colonialization of the New World tropics (13) (SI Appendix).…”

The influence of natural fire and cultural practices on island ecosystems: Insights from a 4,800 year record from Gran Canaria, Canary Islands

“…In particular, the timing and circumstances of human colonization remain the subject of considerable uncertainty. An emerging view, supported by an array of evidence (archaeological, palaeontological, palaeoecological), places colonization towards the end of the first millennium bce (Atoche, 2008; de Nascimento et al., 2020; Rando et al., 2014; Velasco et al., 2019).…”