tl;dr: A large meta-analysis combining 423 studies and 222,829 data points across 23 ecosystem services found that "functional redundancy"—the assumption that ecosystems can absorb species losses because remaining species pick up the slack—is largely wrong, with most benefits scaling continuously with biodiversity. Ocean carbon sequestration showed the strongest dependence on biodiversity of any service measured, though it's also among the least-studied, raising concerns for blue carbon climate strategies. Exceptions exist for services like coastal flood protection, which often rely on a few foundational species rather than overall diversity.