Extinctions in our time
This is a guest article, kindly contributed by Dr. Ben Phalan, an ecologist based at the Parque das Aves in Brazil. The research of Dr. Phalan focuses on how to sustain the needs of agriculture and forestry for human society, whilst preserving biodiversity. You can find Dr Phalan on twitter and Researchgate.
When you come face to face with a species that’s about to go extinct, it hits you in the gut. We are used to thinking about extinctions as something from the long-distant past. I have felt some sadness that I will never have a chance to know a Great Auk (Pinguinus impennis) or an Irish Elk (Megaloceros giganteus), but their dwindling was something that happened a long time ago, and the people who knew them are long dead themselves. Not so with the wave of extinctions that is sweeping through the Atlantic Rainforests of Brazil. I know people who have looked into the eyes of birds that no longer exist. I have met birds that may be among the last individuals of their species, although I devote my time to making sure that is not so.
My meeting with an Alagoas Antwren (Myrmotherula snowi) was in a hilltop rainforest fragment in the northeast of Brazil, the last refuge of this species. He was a small grey bird with a dark beady eye, who perched for a little while, observing me calmly and singing a few hesitant, plaintive notes, before disappearing back into the forest. Our best estimate, based on three years of systematic surveys, is that around ten birds remain, having declined by about 20% each year since those surveys began. Never widespread, this unassuming little bird has died out from the other fragments where it occurred, and is now restricted to just one: Murici, in Alagoas.
It had taken four days in the forest, in the company of biologists Hermínio Vilela and Arthur Andrade, to even find one. A couple of days later, as I waited in one of the known territories for some sign of an antwren, I met a bird guide trudging along the narrow trail with a hot, tired British couple in tow. Ciro is perhaps the most renowned bird guide in Brazil, but they had been unsuccessful in finding the species. “We’ve seen more Alagoas Antwren researchers than Alagoas Antwrens!” sighed the woman, sweaty and crestfallen. “I guess this is what extinction looks like.”
This is what extinction looks like. Outside the protected area, little forest remains. Vast fields of sugarcane bake under the sun, and the ribs of the land show through the endless pasture, where the hooves of cattle have worn thin brown trails crisscrossing the steeper slopes. Most of the deforestation in this region has not been by poor people trying to eke out a living; it’s been with the objective of making a few rich people richer. Exposed to the dessicating wind, the edges of the forest are drying out, and the luxuriant masses of bromeliads, mosses and orchids that once clothed the branches and even the ground are shrinking back to the shady, moist core of the forest. That core is too small to sustain a healthy population of antwrens in the long term, and so they are here, on the brink of oblivion.
Fig 1. A vista of Atlantic Rainforest in Murici, Brazil.
Terms of use: This image is licensed under a Attribution 2.0 Generic license, and is by author Ben Phalan. The image is unedited and the original can be found here
In the past five hundred years, most extinctions of birds have been on islands (1). Island endemics are especially prone to extinction because they have very restricted distributions, have not evolved defenses against mammalian predators and introduced diseases, and in many cases have evolved traits such as flightlessness that make them more vulnerable still. Extinctions of island birds peaked over a century ago. Worryingly, there is now evidence of a new wave of extinctions among continental birds, including the birds of the Atlantic Rainforests of Brazil, where I live and work.
As my recent paper with Pedro Develey of bird conservation organisation SAVE Brasil (2) summarises, the global Red List now counts seven Brazilian birds as globally Extinct, Extinct in the Wild, or Critically Endangered (Possibly Extinct), of which five were from the Atlantic Rainforests. Another two species have not been seen with certainty for decades, while yet more species – including the Alagoas Antwren – are down to a handful of individuals, and face daunting odds against survival. The Atlantic Rainforests, down to some 10% of their original extent, have accumulated an extinction debt: species that did not disappear straight away, but are gradually vanishing, one by one, because there simply isn’t enough forest left to sustain them. Others likely disappeared before they could even be described (3).
The Cryptic Treehunter (Cichlocolaptes mazarbarnetti) was only described in 2014, by which time both the bird and its discoverer, Juan Mazar Barnett, had departed this Earth. Its existence might never have been registered were it not for Mazar Barnett’s sharp eyes and ears. It was a subtle, difficult-to-find bird of the humid hilltop forests of northeastern Brazil, probing for insects and spiders amongst the luxuriant bromeliads that clothe the branches of canopy trees. Its name in Portuguese, gritador-do-nordeste, is heartbreakingly on point, as this excerpt from the species description (4) explains:
‘Gritador’ (meaning ‘screamer’) is an apt name given the loudness of its vocalizations, but it also represents a figure in Brazilian folklore. The story of the ‘Gritador’ is that of two brothers who went hunting and one accidentally shot the other. In desperation, he shot himself, and now his soul sometimes can be heard as it wanders through the forest in the top of the hills, screaming in pain while searching for his brother. A parallel can be drawn with the story of the ‘Gritador’, as C. mazarbarnetti can be heard ‘screaming’ while wandering through the hilltop forest searching in vain for his ‘brothers’, in this case due to the scarcity of the species.
One of the “brothers” of the Cryptic Treehunter was the Alagoas Foliage-gleaner (Philydor novaesi), which inhabited the same forests and even foraged in the same flocks. The species was last seen in 2011. It's an extinction so recent you can watch videos of the species on Youtube. A further species from the northeast of Brazil, the Pernambuco Pygmy-owl (Glaucidium mooreorum), is considered Critically Endangered (Possibly Extinct), and hasn’t been recorded for two decades.
Completing the quartet of missing species from the rainforests of the Pernambuco Centre of Endemism in northeast Brazil is the Alagoas Curassow (Mitu mitu), Extinct in the Wild. Fortunately, in this case, a small captive population exists. All four species suffered from the almost-complete devastation of their rainforest habitats, which were cleared to make way for sugarcane (largely for ethanol production) and cattle pasture.
The Glaucous Macaw (Anodorhynchus glaucus) used to inhabit the region where I now live, in southern Brazil, as well as neighbouring countries. It cracked open Yatay Palm nuts with its powerful bill, and perhaps nested in the steep banks and cliffs along parts of the course of the Iguaçu River. This species was likely driven to extinction by habitat loss, including felling of these palms, not least during the devastating War of the Triple Alliance in the second half of the nineteenth century, during which up to two-thirds of the (human) population of Paraguay were killed. Trapping was also a threat to the species, including for live export to Europe. The Glaucous Macaw was one of the “four blues” exhibited in Berlin in 1900 (5), along with another species that is now Extinct in the Wild, the Spix’s Macaw (Cyanopsitta spixii). Although it is officially still listed as Critically Endangered (Possibly Extinct), the Glaucous Macaw has in reality likely been extinct for almost a century.
Another two species remain on the global Red List as Critically Endangered, but whether or not they still exist is anyone’s guess. The Purple-winged Ground-dove (Paraclaravis geoffroyi) is associated with the infrequent masting events of large native Guadua bamboos. There are no proven records (with photos, audio or other concrete evidence) since the 1980s (6). With the explosion of interest in birds and bird photography in Brazil, it seems unlikely that a species like this, with a large historic range, could remain undetected, but it was a very discreet species and perhaps a few individuals persist in some unexplored bamboo grove in Brazil or Argentina. We are working with a bioacoustics expert, Carlos Araújo, to install sound recorders in the bamboo groves of southern Brazil and northeastern Argentina, in the hope of finding the species again.
The Kinglet Calyptura (Calyptura cristata) is even more of an enigma. There has been just a single multi-observer sighting in the last 130 years, in 1996. The many specimens from the nineteenth century suggest it was not always so rare, but it surely is extremely rare today, if it even still exists (7).
Various additional species teeter on the brink of extinction. Perhaps most worrying is the Stresemann's Bristlefront (Merulaxis stresemanni), which may already have winked out. The known population consisted of a single female in 2019, and since then, only an unconfirmed report from a new site, confirmation of which has been prevented by pandemic restrictions.
Fig 2. A depiction of the Alagoas Curassow (Mitu mitu) by 19th century naturalists Nicolas Huet II and Jean-Gabriel Prêtre.
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The story of each of these species, and indeed of the Atlantic Rainforests as a whole, is one of avoidable tragedy, provoked by short-sightedness, ignorance and greed (8). As Soulé and Wilcox wrote in 1980 (9): “Death is one thing, an end to birth is something else.” The tragedy of extinction goes beyond the loss of individuals – it means that individuals like them, and the roles they play in the fabric of life, can never exist again.
The extinctions I’ve described are all of birds, perhaps the most-observed and best-studied group of organisms on the planet. They do not bode well for the incredible diversity of other species in the Atlantic Rainforests, from bromeliads to velvet worms. For every bird we have lost, we have likely lost, too, a host of smaller, less conspicuous organisms. Most of this wave of extinctions is invisible to us, which makes it easy for extinction deniers to scoff at – but even if we can never fully count the losses, they are no less real for that.
Nevertheless, there are reasons for hope: not the false hope of those who deny that the problem exists, but the hope that comes from determined action. We know that species can be saved from extinction. The Black Robin (Petroica traversi) and the Mauritius Kestrel (Falco punctatus) were brought back, over decades, from populations of just four or five individuals. Populations of both now number in the hundreds. More generally, we know that conservation works (10). The reason biodiversity declines and extinctions continue is that our societies have continued to prioritise a narrow conception of human progress, and have invested few resources in stewardship of nature.
Hopeful signs in the Atlantic Rainforests include the resurgence of younger forests, regrowing on abandoned pastures. They will take a long time to attain the structure and complexity of old-growth forest, but the overall trend is in the right direction, with forest cover increasing as a result of both active and passive restoration. Reintroductions of key species involved in seed dispersal, including the Alagoas Curassow and Black-fronted Piping-guan (Pipile jacutinga), are underway. And there is a new generation of conservationists, including Hermínio and Arthur, who have dedicated their lives and careers to heal some of the harms caused by centuries of exploitation and extraction. In the forests of Murici, we are working hard to find nests of the Alagoas Antwren so we can protect them, to give the species a fighting chance of survival. The odds are not in our favour, but if we succeed, this little grey bird, rather than becoming another sad example of extinction, might instead become a beacon of hope for the recovery of the Atlantic Rainforests.
Fig 3. A pair of glaucous macaw (Anodorhynchus glaucus)
Terms of use: This image is licensed under a Creative Commons Attribution 3.0 Unported. It is attributed to Andrés González. The image is unedited and the original can be found here
Sources and further reading
1. J. K. Szabo, N. Khwaja, S. T. Garnett, S. H. M. Butchart, Global patterns and drivers of avian extinctions at the species and subspecies level. PLoS ONE. 7, e47080 (2012).
2. P. F. Develey, B. T. Phalan, Bird extinctions in Brazil’s Atlantic Forest and how they can be prevented. Front. Ecol. Evol. 9, 624587 (2021).
3. A. C. Lees, S. L. Pimm, Species, extinct before we know them? Current Biology. 25, R177–R180 (2015).
4. J. Mazar Barnett, D. R. C. Buzzetti, A new species of Cichlocolaptes Reichenbach 1853 (Furnariidae), the ‘gritador-do-nordeste’, an undescribed trace of the fading bird life of northeastern Brazil. Revista Brasileira de Ornitologia. 22, 20 (2014).
5. T. Juniper, Spix’s Macaw: The Race to Save the World’s Rarest Bird (Simon and Schuster, 2004).
6. A. C. Lees, C. Devenish, J. I. Areta, C. B. de Araújo, C. Keller, B. Phalan, L. F. Silveira, Assessing the extinction probability of the Purple-winged Ground Dove, an enigmatic bamboo specialist. Front. Ecol. Evol. 9, 624959 (2021).
7. F. Lambert, G. M. Kirwan, The twice-vanishing ‘pardalote’: what future for the Kinglet Calyptura. Neotrop. Birding. 6, 4–17 (2010).
8. W. Dean, With Broadax and Firebrand: The Destruction of the Brazilian Atlantic Forest (University of California Press, Berkeley, CA, 1997).
9. M. E. Soulé, B. A. Wilcox, Conservation Biology: An Evolutionary–Ecological Perspective (Sinauer, Massachussets, USA, 1980).
10. C. M. Lees, A. Rutschmann, A. W. Santure, J. R. Beggs, Science-based, stakeholder-inclusive and participatory conservation planning helps reverse the decline of threatened species. Biological Conservation. 260, 109194 (2021).