There are tens of thousands of species of orchid, making it the second most species-rich plant family on Earth. Their exceptional diversity is driven in part by tightly evolved relationships with pollinating insects and root-boosting fungi. Each species has its own favourite collaborators, a feature that has driven orchids to success, but that also makes them especially vulnerable to extinction when these relationships are perturbed.
So, when the delicate, lemon-scented mignonette leek orchid, unseen since the 1930s, turned up again in 2020, there was cause for celebration. Recent rediscoveries like these – from the ring-tailed glider to the Santa Marta sabrewing hummingbird – are seemingly rare moments of joy amid the rapid loss of many plants and animals around the world. Globally, the number of species deemed to be at high risk of extinction has increased more than five-fold since 2000, and plant species in particular are being lost as much as 500 times faster than would be expected under normal evolution.
Putting a price tag on nature failed. Can radical tactics save it? Yet, evolutionary biologist Aelys Humphreys at Stockholm University, Sweden, doesn’t see rediscoveries as an unmitigated joy.
As she told a recent summit at the Royal Botanic Gardens at Kew, London, the rediscovery of species also constitutes a failure. Extinct species are found again far more often than you might think; at the same time, problems with how and why we declare species extinct are also leading us to underestimate the scale of extinction worldwide. New Scientist spoke with Humphreys about why we need to stop thinking in terms of a species being either extinct or not, and instead take a more nuanced approach to a philosophical problem that has vexed thinkers for thousands of years: how do you prove an absence?
Penny Sarchet: I was surprised to hear you tell the State of the World’s Plants & Fungi symposium earlier this year that every rediscovery is a sort of failure, because it means we‘ve got something wrong. Aelys Humphreys: People react strongly to that message. I don’t want to give the impression that rediscoveries are a bad thing per se: they mean a species is not extinct, so conservation efforts can be renewed.
Fundamentally, it’s a good thing. But the flip side is that an expert decided that a species was extinct and then it turned out that it wasn’t. That can also lead to the erroneous withdrawal of conservation resources from that species.
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