These are species no one really cares about, but they play a key role in the ecosystem.
We're talking about species whose generation time, which is the amount of time (they need) to replace themselves, is 17 to 21 years. So it will be a century before we see any recovery.
Relative abundance is an index of what's out there. We know a lot of these species move, but within what we have the data for, we are seeing this decline range.
Species declines change predator-prey dynamics, energy flow through systems, and ecosystem resilience, stability, function, and form.