Severity of deforestation mediates biotic homogenisation in an island archipelago

Abstract

Anthropogenic-driven species extinctions are radically changing the biosphere. Biological communities may become increasingly similar to or dissimilar from one another via the processes of biotic homogenisation or heterogenisation. A key question is how the conversion of native forests to agriculture may influence these processes by driving changes in the occurrence patterns of restricted-range endemic species versus wide-ranging generalists. We examined biotic homogenisation and heterogenisation in bird communities on the Southeast Asian islands of Borneo, Sulawesi, Seram, Buru, Talaud and Sangihe. Each island is characterised by high levels of avian endemism and unique spatial configuration of forest conversion to agriculture. Forest conversion to agriculture influenced the patterns of biotic homogenisation on five islands. Bird communities became increasingly dissimilar to forest reference communities relative to localised patterns of deforestation. Turnover led to species with larger global range-sizes dominating communities at the expense of island endemics and ecological specialists. Within islands, forest conversion did not result in clear changes to β-diversity, whereas between-island communities became increasingly similar with greater deforestation, implying that patterns of forest conversion profoundly affect biotic homogenisation. Our findings elucidate how continued conversion of forests is causing the replacement of endemic species by a small cohort of shared ubiquitous species with potentially strong negative consequences for ecosystem functioning and resilience. Halting reorganisation of the biosphere via the loss of range-restricted species and spread of wideranged generalists will require improved efforts to reduce the impacts of deforestation, particularly in regions with high endemism.

Biodiversity monitoring as a baseline for PROPER biodiversity protection program of PT. Geo Dipa Energi Dieng, Central Java, Indonesia

“…Furthermore, 86.40% of the bird abundance was represented only by ten dominant species, and more than two-thirds (75.10%) of the dominant species guild were insectivorous and ubiquitously distributed (Figure 4), showing a homogeneous community pattern. Similar results were also reported by Mitchell et al (2022), that investigated the bird guild turnover across a gradient of deforestation and found the proportion of insectivores negatively correlated with the forest cover in Talaud and Seram Island, with an approximately 2.5% proportion increase per 10% forest cover loss. In contrast, the frugivore, the essential forest seed dispersers, and the fruiting tree-dependence guild were positively correlated with the forest cover.…”

“…In addition, another plausible cause for the low number of frugivores may be the hunting pressure, such as that exerted on species of Wallacean parrots that are popular in the cagebird trade (Setiyani and Ahmadi 2020). Furthermore, insectivores presumably thrived because the guild has a lower degree of dietary specialization, thus less susceptible to habitat degradation (Mitchell et al 2022). However, the insectivorous speciesspecific sensitivities variation should be noted (Hamer et al 2015;Stratford and Stouffer 2015), requiring further investigation.…”

“…Furthermore, the spread of cosmopolitan species into newly accessible areas expands their range and population, accelerating the colonization process (Dyer et al 2016). Due to their small ecological niche, specialized species are disproportionately eliminated from the ecosystem (Socolar et al 2016;Vatani et al 2017;Reside et al 2019) There is a growing body of evidence showing the anthropogenic impact on several taxa homogenization, including birds (Mitchell et al 2022), herpetofauna (Palmeirim et al 2017), insects (Knop 2016), freshwater fish (Bezerra et al 2019), river and lake macroinvertebrates (McGoff et al 2013;Liu et al 2022), mammals (Lezzi et al 2021;Arce-Penna et al 2022), also vegetation (Haider et al 2017). These simplifications potentially adversely impact the ecological services since the loser species potentially serve critical roles in the ecosystem (Holl et al 2022).…”

Foundation species canopies affect understory beta diversity differently depending on species mobility

“…Therefore, beta diversity is being increasingly considered in regional conservation planning (Socolar et al, 2016; Suurkuukka et al, 2012). While studies continue to address the consequences of beta diversity, additional efforts are focusing on the mechanisms that drive beta diversity changes (Maxwell et al, 2022; McDevitt‐Irwin et al, 2021; Mitchell et al, 2022).…”

Logged tropical forests have amplified and diverse ecosystem energetics

“…Mammal populations collapse because they are more vulnerable and avoid humans, and there is no suite of mammal generalists that can step in 27 , 28 . Birds show a more modest decline, to levels similar to those observed in old-growth forests, as there is a broad suite of generalist species that are able to adapt to and exploit the habitat types across the disturbance gradient, and because their small size and mobility render them less sensitive to human activity 29 . There is a consistent decline in the oil palm in ESWI for birds and especially for mammals, indicating a substantial increase in ecosystem vulnerability in many pathways.…”