(ORDO NEWS) — Human activity leads to the fact that plants and animals die out at a terrifying rate. From habitat loss, overfishing and poaching to global warming and pollution, species are dying out faster than we can imagine.
A new study by ecologist Heidi Hernandez-Yanez and two colleagues from the Alexander Center for Applied Population Biology at Chicago’s Lincoln Park Zoo has uncovered commonalities among endangered plants, birds and mammals – and comes up with surprising results.
“Certain combinations of life history traits and demographics can make a population more prone to extinction than others,” Hernandez-Yanes of the Woodwell Climate Research Center and colleagues explain in their paper.
But as they point out, until recently, few studies have tested predictions of what makes one species more vulnerable to another in different taxonomic groups using real data on a global scale.
The nature and timing of survival, growth, and reproduction all determine whether plant and animal populations can withstand or adapt to the onslaught of anthropogenic environmental change.
In the new study, Hernandez-Yanez and colleagues collected data on the growth rate, lifespan and reproduction of 159 species of herbaceous plants, trees, mammals and birds, and also checked the current status of endangered species according to the IUCN Red List – the world’s main list of endangered species.
“Despite a relatively small sample of species, we found that species with certain demographic characteristics are more at risk of extinction than others, and that important predictors differ between taxonomic groups,” the trio of researchers write.
For example, mammals with longer generation periods are most at risk of extinction, perhaps because the longer it takes for species to mature and reproduce, the more difficult it is for them to adapt to rapid environmental changes – and especially if animals only breed once in a lifetime.
Meanwhile, birds that breed frequently and grow rapidly – from chicks to mature adults – are more vulnerable to extinction, which turned out to be somewhat unexpected – you would think that the production of a large number of offspring increases the chances of the species to survive.
In contrast, other studies have shown that birds with smaller clutch sizes are at greater risk of extinction, so the data varies, and the differences may reflect multiple ways of measuring reproduction, the researchers note.
In terms of plant species similarity, soft-stemmed herbaceous perennials – those that die off before winter and bloom in spring and summer – are more likely to die if they mature early and have a high survival rate as juvenile seedlings. However, no clear patterns were observed for endangered woody trees.
“After all, deforestation for crops and urbanization do not differentiate between tree species,” write Hernandez-Yanes and colleagues.
The findings complement those of another recent study on extinction risk prediction, which showed that the most vulnerable are species at the top of the food chain with small populations or a small geographic range.
However, such studies are often limited by the IUCN Red List, which covers only a subset of endangered species – mostly in biodiversity hotspots – and is highly skewed towards birds and mammals.
Amphibians, for example, are among the most endangered species: a third of all known amphibian species are threatened with extinction, and thousands of species are not yet assessed by the IUCN or there is not enough data to do so.
And that’s not to mention the insects and other invertebrates that pollinate plants, disperse seeds, and carry nutrients throughout ecosystems, and the countless yet-to-be-discovered species that are dying out faster than we can describe them.
“Most of these extinctions go unrecorded, so we don’t even know what species we’re losing,” ecologists Elizabeth Boakes and David Redding wrote in a 2018 paper, describing “incalculable losses.”
All this means that no matter how hard scientists try, we are likely to underestimate the true extent of biodiversity loss and the risk of extinction. Nearly 350 herbaceous plant species analyzed in this study did not have IUCN status.
Conservationists refuse to bury their heads in the sand when the threat is close and the stakes are high. We know what needs to be done to contain the loss of biodiversity and protect endangered species; the question is whether we can turn the tide of extinction before it’s too late.
Recognizing this, Hernandez-Yanez and his colleagues hope that a better understanding of which traits put plants and animals at the highest risk of extinction will help in the conservation effort.
The results obtained can be used to assess which species are more or less vulnerable to extinction, especially in cases where abundance data are not available.
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