Final answer:
The collapse of biomass in Amazonian rainforest fragments leads to a decline in species richness due to habitat destruction and deforestation, resulting in a reduced biodiversity.
Step-by-step explanation:
The result of the biomass collapse in Amazonian fragments is a decline in species richness. This is due to habitat destruction caused by deforestation, mainly for timber and agriculture. As these fragments of rainforest shrink, the biodiversity within them is severely reduced. Biodiversity hotspots such as Amazonian rainforests are essential because they contain high species diversity and many species that are endemic to these areas. With the loss of these habitats, we see a clear decline in biodiversity, not an increase. Similarly, the notion that ecosystem stability might improve is incorrect since the removal of species from an ecosystem generally results in diminished resilience to environmental changes and a loss of ecosystem services. Finally, expansion of forest cover is unlikely as deforestation is typically followed by land conversion for agricultural use, rather than reforestation.