For a fixed total protected area, planners can protect it as one large contiguous reserve, or split the same budget across several smaller, separated reserves. Neither is objectively correct — the trade-offs run in opposite directions:
- One large reserve — low edge-to-core ratio (more buffered interior habitat), and the only option that can hold a species needing a big contiguous home range. But it concentrates the entire protected population in one place: a single fire, disease outbreak or poaching incursion there can wipe out everything at once.
- Several small reserves — spread that risk (a disaster in one leaves the others untouched), and if scattered across a varied landscape they can collectively capture more distinct habitat types. But each has proportionally more edge, none can support a large-range species, and without corridors the separate populations can't exchange migrants.
Adjust the reserve count at a fixed total area and watch the four live indicators move in opposite directions — there is no setting that wins on every metric at once.