According to ecological theory, maximum services are delivered when:
Ecosystem services are most reliably sustained when multiple species make substantial contributions rather than when function is concentrated in one dominant species. Even contribution raises functional evenness: different taxa participate in production, decomposition, pollination, nutrient retention, or trophic regulation, reducing dependence on a single vulnerable contributor. It can also strengthen the “insurance effect,” because species respond differently to drought, disease, or disturbance; decline of one contributor may be offset by another. This does not mean every species performs an
Ref: NCERT Biology Class 12, Ch. 15 Biodiversity and Conservation