Conserve ecosystems, not individual species

For millions of years, mammal species have waxed and waned. Yet their broader ecological roles have helped ecosystems prevail through fluctuating environments, according to a study published in the journal Science.

“That means that, even when the ecosystems had a huge replacement of species due to extinction and speciation, the ecological structure remains unaltered for long periods of time,” explains lead author Fernando Blanco from Germany’s Museum für Naturekunde Berlin.

“Only dramatic changes in the environment force the ecosystem into a new ecological structure, while the species composition changes gradually.”

The findings support notions that, rather than focus exclusively on individual endangered or iconic species, conservation efforts should aim to protect the diversity of the animals’ broader functional traits.

“The conviction is that conserving a higher order phenotypic diversity should help to stabilise ecosystems in the face of disturbances (the ‘insurance effect’), increasing the persistence of ecosystem functioning,” the authors write in their paper.

To gain a deep-time window into ancient life, they turned to a new fossil dataset of large mammals that lived on the Iberian Peninsula in southwest Europe, one of the most complete and best-studied records covering the past 21 million years.

They used network analysis to characterise the dynamics of the mammal ecosystem structure using two different approaches: grouping communities that had either similar species composition or similar ecological roles.

Ecological roles of nearly 400 mammals were determined according to size, diet and type of locomotion, providing “functional entities” based on combinations of these three traits.

For example, one community might include many different plant-eating species that browse for food – bonding them functionally – and another community could have fewer plant eaters, with only some browsers while the others graze.

The analysis revealed high instability of individual species while functional entities endured. Importantly, this endurance was related to the functional richness of the broader system rather than that of the constituent species.

Only major climatic disturbances were able to force ecosystems into reorganisation, such as glaciations or the Mediterranean Sea drying up, so today’s Iberian community shares structural elements with mammalian communities spanning the past eight million years.

The insights should help inform long-term conservation strategies, according to the team.

“If the past is useful to illuminate the future,” they write, “our paleobiological perspective further emphasises the gap between conservation policies that minimise extinctions and those that target ecosystem functioning and its benefits to people.”

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