In biodiversity conservation, the “SL > SS principle”
that a single (or few) large habitat patches (SL) conserve more species
than several small patches (SS) is used to prioritize protection of
large patches while down-weighting small ones. However, empirical
support for this principle is lacking; most studies find SS
> SL. We propose a research agenda to resolve this dilemma
by asking, “are there consistent, empirically-demonstrated conditions
leading to SL > SS?” We develop a hypothesis to answer
this question, the “SLOSS cube hypothesis,” which predicts SL
> SS only when all three of the following are true:
between-patch movement is low, population dynamics are not influenced by
spreading-of-risk, and large-scale across-habitat heterogeneity is low.
We then propose methods to test this prediction. Many tests are needed,
comparing gamma diversity across multiple landscapes varying in number
and sizes of patches. If the prediction is not generally supported
across tests, then either the mechanisms leading to SL > SS
are extremely rare in nature, or they are outweighed by countervailing
mechanisms leading to SS > SL (e.g. lower competition or
higher immigration in SS), or both. In that case, the SL >
SS principle should be abandoned.
A blueprint towards accounting for the management of ecosystems
