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

Abstract

The extinction of iconic species such as the dodo and the deforestation of Easter Island are emblematic of the transformative impact of human colonization of many oceanic islands, especially those in the tropics and subtropics. Yet, the interaction of prehistoric and colonial-era colonists with the forests and forest resources they encountered can be complex, varies between islands, and remains poorly understood. Long-term ecological records (e.g., fossil pollen) provide the means to understand these human impacts in relation to natural change and variability pre- and postcolonization. Here we analyze paleoecological archives in forested landscapes of the Canary Islands and Cabo Verde, first colonized approximately 2,400 to 2,000 and 490 y ago, respectively. We demonstrate sensitivity to regional climate change prior to human colonization, followed by divergent but gradual impacts of early human settlement. These contrast with more rapid transformation in the colonial era, associated with significant increases in anthropogenic pressures. In the Canary Islands, at least two native tree taxa became extinct and lowland thermophilous woodlands were largely converted to agricultural land, yet relictual subtropical laurel forests persisted with limited incursion of nonnative species. In Cabo Verde, in contrast, thermophilous woodlands were depleted and substituted by open landscapes and introduced woodlands. Differences between these two archipelagos reflect the changing cultural practices and societal interactions with forests and illustrate the importance of long-term data series in understanding the human footprint on island ecosystems, information that will be critically important for current and future forest restoration and conservation management practices in these two biodiversity hotspots.

The vanishing and the establishment of a new ecosystem on an oceanic island – Anthropogenic impacts with no return ticket

“…These changes are an unequivocal signal of animal husbandry in the Lake Funda catchment. Similar trends are found on other Azorean sedimentary records (Connor et al, 2012;Raposeiro et al, 2021b;Rull et al, 2017) and archipelagos (Castilla-Beltrán et al, 2021). The strong human impact combined with climate instability acted synergistically and transformed the Lake Funda ecosystem abruptly.…”

“…However, human disturbances (i.e. deforestation) had a longer-lasting impact on the pristine vegetation on islands than climatic changes and volcanic activity (Castilla-Beltrán et al, 2021;Nogué et al, 2021). This is particularly relevant for Flores Island during the last millennium (Andrade et al, 2021;Connor et al, 2012;Raposeiro et al, 2021b).…”

Time-calibrated phylogenies reveal mediterranean and pre-mediterranean origin of the thermophilous vegetation of the Canary Islands

“…The effect of island extinction in crown age estimates may be particularly pronounced in the thermophilous woodland because of multiple causes: (i) erosion and subsidence of flat, oldest islands (Fuerteventura, Lanzarote), which may previously have harbored large areas with this vegetation type (Fernández-Palacios et al 2008, Martín Osorio et al 2011); (ii) geological dynamics (eruptions, earthquakes, mega-landslides) , García-Olivares et al 2017; and most importantly (iii) human land use and destruction of original vegetation (only 11 % currently preserved) between 200 and 600 m.a.s.l. (Fernández-Palacios et al 2008, Castilla-Beltrán et al 2021. This extreme reduction of populations, continuing even in our lifetimes, makes thermophilous vegetation the most threatened ecosystem in the Canary Islands (Castilla-Beltrán et al 2021).…”

“…Chronologically, African human groups colonized the seven the islands, who mostly settled around 2000 years ago, and then a more severe deforestation took place since colonization by European groups (Fernández-Palacios et al 2008). As a result, currently only 11 % of the original thermophilous woodland is estimated to remain (Fernández-Palacios et al 2008, Castilla-Beltrán et al 2021.…”

“…(Fernández-Palacios et al 2008, Castilla-Beltrán et al 2021. This extreme reduction of populations, continuing even in our lifetimes, makes thermophilous vegetation the most threatened ecosystem in the Canary Islands (Castilla-Beltrán et al 2021). This is illustrated by the few remaining individuals of non-endemic species in the thermophilous vegetation belt (Pistacia lentiscus, Ephedra fragilis), many critically endangered species (e.g., Anagyris latifolia, Crambe scoparia Svent., Cheirolophus duranii (Burchard) Holub, Dracaena tamaranae Marrero Rodr., R.S.Almeira & M.Gonzáles-Martin, Echium handiense Svent., Gymnosporia cryptopetala, Helianthemum gonzalezferreri Marrero Rodr., Helianthemum bramwelliorum Marrero Rodr., Solanum lidii Sunding, Solanum vespertilio Aiton subsp.…”