“Forest fragmentation in the Amazon rainforest increases the vulnerability of forests to droughts and fires and negatively affects many animal species.”

Changes in weather and land use are transforming the spatial and temporal characteristics of fire regimes in Amazonia, with important effects on dense, open-canopy, and transitional forests across the basin. These observations suggest that climate-mediated forest flammability is enhanced by landscape fragmentation caused by deforestation, as observed for open and transitional forests in the eastern Amazon Basin.

The authors report that forest fragmentation changes tree architecture and allometry, and that these edge effects exacerbate biomass loss in fragmented Amazonian forests. They write that long-term measurements show fragmented forests in Central Amazonia experience a dramatic loss of aboveground tree biomass caused by the mortality of large trees, and that edge effects intensify this loss.

Anthropogenic disturbance had a negative effect on allelic richness, but not on gene diversity. Habitat fragmentation had a negative effect on genetic variation, whereas habitat degradation had no effect. When we examined the individual effects in fragmented habitats, allelic richness and gene diversity decreased, but this decrease was strongly dependent on certain plant traits.

During the drought, average annual tree mortality rose significantly in both forest edges and interiors. After the drought, tree mortality declined in all plots, but most dramatically on edges. The paper also states that forest edges lost a significantly higher proportion of large trees than forest interiors, showing that drought effects in fragments were complex and that edges were especially dynamic.

The Amazon basin is experiencing rapid forest loss and fragmentation. Fragmented forests are more prone than intact forests to periodic damage from El Niño–Southern Oscillation (ENSO) droughts, which cause elevated tree mortality, increased litterfall, shifts in plant phenology, and other ecological changes. We argue that the synergistic effects of forest conversion and climatic stress can create positive feedbacks among forest loss, fragmentation, fire, and regional climate change.

The paper states that episodic wind disturbances cause considerable spatial and temporal variability in tree mortality and other correlated edge effects. It also says the study assesses how edge effects alter Amazon forest dynamics, plant community composition, invading species, and carbon storage in the world's largest and longest-running experimental study of habitat fragmentation.

The 2023–2024 drought, surpassing previous records, combined with forest fragmentation, has dramatically heightened fire vulnerability. Analysing the Tropical Moist Forest and Global Wildfire Information System datasets, the paper reports a 152% surge in forest disturbances from deforestation and degradation in 2024, reaching a 2-decade peak of 6.64 million hectares.

The paper reports that annualized mortality near edges was more than twice that in forest interiors during the baseline interval, and that mortality remained higher or more variable near edges during and after the drought. It also states that newly created edges experience a dramatic pulse of tree mortality, followed by increased recruitment of pioneer and secondary species.

The 2023–2024 drought, surpassing previous records, combined with forest fragmentation, has dramatically heightened fire vulnerability. This degraded state also sets in motion a series of detrimental feedback loops: the increased tree mortality due to edge effects acts as readily available fuel for fires, while fragmentation facilitates greater access for hunting and resource extraction, both of which contribute directly to tree mortality and heightened fire incidence.

This study showed that landscape fragmentation interacts with severe droughts to alter the Amazon forest fire regime. The authors report that open and transitional forests, which are more fragmented and deforested, experienced higher fire frequency and larger burned area than dense forests, and conclude that climate-mediated forest flammability is enhanced by fragmentation caused by deforestation.

In the Amazon region, it is known that the probability of the occurrence of forest fires can change with the distance to the edge of the forest fragment in relation to the core of that fragment. Within a few days of logging operations, drastic changes in humidity and temperature levels are evident in relation to the interior of the forest. Forest edges show high tree mortality, while fragmented forests are more susceptible to the occurrence of fires due to the edge effect. Due to the accumulation of dry materials, droughts increase the fire risk, in particular in the years of an El Niño event.

A new study ... provides the first quantitative assessment of how environmental policies on deforestation, along with forest fires and drought, have impacted the diversity of plants and animals in the Amazon. Since 2001, between 40,000 and 73,400 square miles of Amazon rainforest have been impacted by fires, affecting 95% of all Amazonian species and as many as 85% of species listed as threatened in the region.

Ongoing deforestation and fragmentation of forests in the Amazon help create tinderbox conditions for wildfires in remnant forests. The researchers found that fragmented forests are more susceptible to the negative impacts of drought and fire and that drought leads to an increase in fuel such as leaves and branches.

The report says fragmented forests are more susceptible to the negative impacts of drought and fire, and that drought leads to an increase in fuel such as leaves and branches. It also quotes the researchers saying severe drought makes fires more intense, creating a second tree mortality threshold.

The thesis reports that a significant proportion of studies showed negative, positive, and nonsignificant fragmentation effects on species richness. It also notes that declines in richness near habitat edges are more severe than responses to fragmentation per se, and that the negative edge effect is stronger in the tropics than in temperate zones.

Across Amazon ecology literature, fragmentation is widely recognized to reduce habitat quality for many forest-dependent animals through edge effects, isolation, and changes in microclimate. However, some generalist or disturbance-tolerant species can persist or even increase in fragmented landscapes, so the effect is not uniform across all animal species.

This record points to a study on Amazonian nonvolant mammals and habitat fragmentation, but the accessible page does not provide enough details here to verify the specific effect on species vulnerability or drought and fire susceptibility. It is relevant background on Amazonian fragmentation impacts, but not direct evidence for the claim.