In rivet hypothesis, species loss impacts:
The rivet hypothesis predicts accumulating, often stepwise deterioration as species are removed. Individual losses may initially have small effects, yet each removes part of the system's functional support, so resilience and performance decline and eventual collapse becomes increasingly likely. Species richness counts taxa but does not show their abundance, traits, or interaction strengths. Dominant species may control bulk process rates, rare species may provide specialized functions or future insurance, and predators can restructure whole food webs through indirect effects. Functional groups summarize role overlap, while keystone effects identify unusually strong influence. Separating these dimensions explains why equal losses of richness can have very different ecological consequences and why conservation cannot rely solely on the number of species remaining. In this context, the keyed term, Gradual, stepwise decline, identifies the relevant mechanism or quantitative relationship and links the observed pattern to its underlying ecological cause. The distinction is testable by measuring changes in organisms, resources, or process rates through time rather than relying on the label alone.
Ref: NCERT Biology Class 12, Ch. 15 Biodiversity and Conservation