A 30-year albatross record puts climate mitigation ahead of evolution for population persistence

The obstacle is generation time. Because long-lived species breed slowly, the environment can deteriorate and a population can fall before evolutionary responses have had time to affect its trajectory ^[10]. Evolutionary rescue, the case where adaptive change lets a population avoid extinction after its environment worsens, is often proposed as a buffer against biodiversity loss as the climate changes ^[11].

The model was built so that selection emerged from the birds. It combined albatross demography, the inheritance of traits from parents to offspring, and climate projections, and it tracked how differences among individuals in physical traits, behavior and breeding timing fed into survival and reproduction ^[4]. Uncertainty in population change and natural climate variability were carried through as well ^[5]. "Some traits, such as wing length, can help young birds survive, but the key question is whether evolutionary changes in those traits can happen fast enough to keep pace with climate change," said co-author Joanie Van de Walle of the Universite du Quebec a Rimouski ^[14].

Run under the relatively stable climate of the past, letting the population adapt produced larger projected populations. Under future warming scenarios, adaptation generally did not prevent decline ^[7]. The inheritance channel itself did little to lower extinction risk ^[8]. "Evolution can help populations cope with environmental change, but our results show that it has limits," said Jenouvrier ^[12].

The halving is the number readers will carry away, so it is worth being exact about what it is. The eco-evolutionary model produced it by running contrasting emissions levels ^[17]. Nobody watched it happen in a colony. The phys.org account reports the reduction as approximately half and does not give the baseline probability or say which emissions scenarios were compared ^[18]. Halving a one-in-twenty risk and halving a one-in-two risk describe different management problems.

Mitigation and adaptation are not competing levers inside this model. The authors report that when climate change is sufficiently limited, evolutionary responses can contribute to persistence, and that under stronger warming they generally are not enough ^[16]. They also point to how strongly selection favors the traits in question and how fast the climate changes, not only to whether traits are heritable ^[9]. "Reducing future climate change by decreasing greenhouse-gas emissions slows population decline and enables evolutionary adaptation to promote population persistence," said Marika Holland, a scientist at the National Center for Atmospheric Research ^[15].

One caution on scope. This is one species, a pelagic seabird that spends most of its life far out over the Southern Ocean, with more than three decades of demographic and phenotypic data behind the model ^[1][2]. The result travels as a claim about long generation times, and whether the same ordering of mitigation and adaptation holds for other slow-breeding animals is a question their own data would have to answer.