Effect of canal blocking on biodiversity of degraded peatlands: Insight from West Kalimantan

PLOS One | https://doi.org/10.1371/journal.pone.0334014 October 8, 2025 13 / 23 Habitat types were likely to generate differences in habitat heterogeneity, with greater vegetation complexity affecting the findings because higher wildlife species richness indices were spotted in less disturbed and disturbed peat forests. Greater habitat complexity, including more diverse and varied vegetation, typically increases food and shelter avail- ability for wildlife, fostering reproduction and survival, thus elevating species richness and total abundance [56–59]. Increased habitat complexity includes increasing number of canopy layers more likely to facilitate niche necessity between species. Regarding observation month, the dry season August survey identified higher species richness indices in all habitat types than the wet season survey in May and forested habitat still had greater richness than non- forested habitat. During the dry season, wildlife faces severe scarcity of food, water, and shelter, compelling species to relocate to habitats with more stable resources [60–63]. The increase in species richness indices from May to August across all rewetting sites demonstrates that peatlands play an important role in providing resources for wildlife, espe- cially water, even at the peak of the dry season. Therefore, protecting peatlands from further disturbance and improve its quality is crucial. Temperatures in forested habitats were lower, and humidity was higher, on average, than non-forested habitat. With

higher means of humidity, make the habitat warm and humid at the same time, typical traits for tropical forest near equator such as Indonesia [64–66]. Such habitat characteristics influence wildlife fitness, and impacts can vary across species and populations. An increase in temperature outside of a species’ tolerance range may affect survival rates, leading to a decline in population [67]. Amphibians are greatly influenced by their environment, where shifts in temperature and mois- ture levels can impact survival, distribution, and population size [68,69]. Reptiles are temperature sensitive and increasing temperatures could affect their thermoregulation patterns and reproduction [70]. Additionally, temperature also impacts their population abundance, behaviour, and energetic costs of numerous bird and mammal species [67,71]. Higher wildlife richness, diversity, and evenness in forested habitat demonstrates that the habitat provides more ideal temperature and humidity for most of species than open habitat such as estate crop and disturbed wet shrub. Understory vegetation holds significant importance, serving as both food for herbivores and shelter for ground-nesting birds and small mammals [72]. In addition, understory also offers additional niches and shelter, providing protection against heat and predation for herpetofauna [73–76]. Despite the vital role understory plays in wildlife diversity, it does not necessarily imply that habitats solely comprised of understory cover are most suitable for wildlife. Our results show that

complex habitats with multiple vegetation layers may be more advantageous for some species. Understory becomes par- ticularly crucial in plantations, which typically consist of homogeneous species. The presence of understory cover adds an additional layer to the habitat. Thus, when intensive plantation management removes the understory layer, often consid- ered as weeds, it will reduce the occurrence of fauna in the habitat [77]. Dominance and evenness are two interconnected concepts. Evenness pertains to how similar the abundances of co-existing species are, while dominance of one or a few species is evident when there is unevenness in species abun- dances [78]. When one species dominates a habitat, there is low evenness, whereas the absence of dominant species suggests high evenness. The value of Pielou’s Evenness and Berger Parker Dominance Index illustrates that estate crop has lower evenness, thus lower diversity, because it is dominated by the Yellow-vented Bulbul (Pycnonotus goiavier). In May, we observed 55 individuals of this bird species, while in August, the count was 49 individuals. According to the GLM analysis, there is an inverse correlation between the Berger Parker Dominance Index and the diversity of vegetation spe- cies. The homogeneous palm oil plantation may only provide resources for small range species. The Yellow-vented bulbul as a generalist species demonstrates adaptability to various habitats including mangroves, secondary forests, rural, and

urban areas [79]. The bulbul appears to have effectively adapted to the resources provided in palm oil plantations by utiliz- ing insects and palm oil fruit remnants as food sources [80]. Consequently, it emerged as the most sighted species within the oil palm plantation. In other habitat types, we also encountered the Yellow-vented Bulbul, but the abundance was not as massive as we found in the palm oil plantation. By reviewing the pattern of dominance and evenness indices, we can infer that a complex habitat tends to promote greater evenness.