Tag Archives: tropics

A new species of bird discovered in Brazil has a green head, yellow belly, and a high risk of going extinct soon

An international team of ornithologists reports discovering a new species of bird in north-eastern Brazil. Sadly, the forests it calls home have been almost completely cut down.

The black-throated trogon (Trogon rufus). Image credits Moisés Silva Lima.

The new species has been christened the Alagoas black-throated trogon (Trogon muriciensis), and is part of the Trogonidae family of tropical birds. Comprising around 43 species and almost 110 subspecies, the trogons are some of the most colorful birds in the world — at least, the males. They sport patterns of various colors including iridescent green, blue, violet, and purple, with bright red, orange, or yellow abdomens. The females have to make do with gray or brown feathers.

Bird is the word

Trogon rufus is easy to distinguish by the unique combination of a green head in males, brown in females, and a yellow belly,” said Jeremy Kenneth Dickens, a researcher at the Museu de Zoologia da Universidade de São Paulo and the Fundación Para La Tierra, and lead author of the study.

“However, with the collection of more material, it soon became recognized as notoriously variable across its distribution.”

The trogon family was first described in 1788 with the black-throated trogon (Trogon rufus), which is quite common in the lower and mid-levels of humid forests spanning from Honduras to northern Argentina.

After its initial description, however, more observations of this bird made it clear that its characteristics varied quite significantly across its range. In other words, it was possible that what we were seeing wasn’t a single species, but rather a family of species.

In order to get to the bottom of it, the team looked at 547 male and 359 female trogon specimens from the collections of 17 different museums. They factored in morphological, vocal, and genetic datasets, as well as spectral and digital data of their plumage, to establish the family tree of the trogons.

All in all, they identified five populations that show signs of reproductive isolation — in other words, five groups of trogons that don’t interbreed and show differences in traits involved in species recognition such as plumage, behavior, or song. Four of these were already known as the Amazonian black-throated trogon (Trogon rufus), the southern black-throated trogon (Trogon chrysochloros), the (somewhat fancily-named) graceful black-throated trogon (Trogon tenellus), and the Kerr’s black-throated trogon (Trogon cupreicauda).

The fifth population, however, wasn’t identified as a distinct group previously. It makes its home in the mountainous stretches of the Atlantic Forest in the Brazilian state of Alagoas (hence its name). This group is distinct enough morphologically, genetically, and through behavior such as song to represent a completely new species, the team explains. It can be distinguished from most other trogon species by the combination of a green head and bright yellow belly.

“It is only known from Estação Ecológica de Murici in the Alagoas state, at just over 500 m elevation, where it occurs in mid-levels of the montane Atlantic Forest,” the team explains.

“It was presumably once more widespread throughout this habitat in the Pernambuco Centre of Endemism before the deforestation of the region.”

According to the team, finding records and individuals of this species in a single, relatively small area, does not bode well. They further explain that during fieldwork in 2019 in the region, they only found 20 individuals and “explicitly avoided” collecting more than one specimen for further study after seeing how low their numbers appeared to be.

The team recommends that the Alagoas black-throated trogon is immediately listed as Critically Endangered, as only around 30 km2 of forest remains in their known range. These forests are also “mostly small fragments and not all suitable for this species,” casting further doubt on their ability to recover.

The paper “Species limits, patterns of secondary contact and a new species in the Trogon rufus complex (Aves: Trogonidae)” has been published in the journal Zoological Journal of the Linnean Society.

Life in the tropics could become impossible if we don’t reduce our emissions

If we don’t limit global warming to less than 1.5ºC the tropics could become uninhabitable within a few decades. Life in the equatorial region, home to about 43% of the world’s population, could also become intolerable.

Image credit: Flickr / Hanming

Countries vowed to limit temperature increase to 2ºC, ideally aiming at 1.5ºC, in what is called the Paris Agreement. Half a degree may not seem relevant but it actually is for many regions of the planet. The global average temperature has already risen over 1ºC compared to pre-industrial times, and if we want to limit further increase, we need to take drastic action — fast.

In a new study, Princeton University researchers wanted to see how a warming climate would affect our ability to inhabit the world’s hottest places. They focused on a measure known as the wet-bulb temperature, which accounts for heat and humidity. The body cools itself through sweating and the evaporation of sweat from the skin. But this has a limit. Scientists argue that humans can tolerate a wet-bulb temperature of up to 35ºC (95 ºF). Beyond that, we are in trouble. 

The human body normally has a stable internal temperature of around 37ºC (98.6 ºF). Skin temperature has to be a bit lower so to allow core heat to flow to the skin. If it’s not, a person’s internal temperature could rise quickly. “If it is too humid our bodies can’t cool off by evaporating sweat,” Yi Zhang, study-lead, told The Guardian. “High body core temperatures are dangerous or even lethal.”

The researchers focused on how global warming could affect wet-bulb temperatures in tropical areas such as the Amazon rainforest, the Indian peninsula, parts of Southeast Asia, and a large part of Africa. They found that even before the 1.5ºC threshold, there could be adverse health effects. But after the threshold, things can get very bad very fast. Mojtaba Sadegh, an expert in climate risks at Boise State University that wasn’t involved in the study, told The Guardian that if this limit is breached, “infrastructure like cool-air shelters are absolutely necessary for human survival.” Given that much of this effect would happen in developing countries, that seems very unlikely to develop.

Climate urgency

The new research is just the latest scientific warning over the severe dangers posed by extreme weather events. A study last year found the impact of high temperatures on hospitalizations due to cardiovascular diseases has increased in Australia over the past two decades. Cardiovascular diseases are the main cause of mortality and morbidity worldwide.

This highlights the need for further climate action to tackle the growing greenhouse gas emissions. New climate pledges are expected this year by the United States, China and the European Union, the world’s largest emitters. With the world’s current efforts, climate experts estimate the global average temperature could reach 3ºC by the end of the century. 

The study was published in the journal Nature GeoScience. 

In 10 to 20 years, it will be so hot that tropical trees live shorter lives

It’s not the best time to be a tropical tree, as rising average temperatures risk impacting their lifespan.

Image credits Roel Brienen.

A new study explains that the longevity of trees at the tropics is shortened by higher temperatures. The findings help further our understanding of how climate change will impact ecosystems in the area and its effects on the rest of the planet. The team argues this is the first direct evidence that tropical trees experience shorter lives in hotter environments, and that forests all around the world will be affected.

Over-temperatured

“Many regions in the tropics are heating up particularly rapidly and substantial areas will become warmer, on average, than approximately 25 °C,” says Professor Manuel Gloor at the University of Leeds, a co-author of the paper.

“Our findings – which are the first to demonstrate that there is a temperature threshold – suggests that for trees in these regions, their longevity is likely to be negatively affected.”

The temperature above which trees become affected is 25 °C, the paper explains. This result is based on four years’ worth of tree ring data recovered worldwide. Roughly 100,000 trees from 400 species in 3,000 sites across the planet formed the dataset. All in all, the team reports that although tropical trees grow twice as fast as those in cold areas, they also live shorter lives (186 years vs 322 years on average).

Average temperatures in tropical forests today sit between 21 °C and 30 °C depending on location. These averages will rise alongside the rest of the world to around 2.5 °C above pre-industrial levels over the next 10 to 20 years. The effect this will have on trees varies depending on exactly how much hotter it gets. Changes in precipitation patterns (another effect of climate change) are going to exacerbate this ever further.

Substantial areas of today’s rainforests will see significantly lower tree longevity. They only cover 7% of the Earth’s surface, but harbor around 50% of its species of plants and animals, and a corresponding 50% of the planet’s carbon stocks. Any change here will have strong, global echoes for habitats, air quality, and carbon scrubbing ability.

“These results are a warning sign that, along with deforestation, global warming adds extra stress on the Earth’s tropical forests,” says Dr Roel Brienen from Leeds, paper co-author.

“If tropical trees die earlier, this will affect how much carbon these forests can hold, raising concerns about the future potential of forests to offset CO2 emissions from fossil fuel burning. It could also cause changes in biodiversity and a decrease in the number of species on the planet.”

Tropical forests in South America are closest to this threshold, but they’re not the only ones at risk. Even the Congo Forest in west Africa, the world’s second largest but with lower average temperatures, will be affected.

The saddest finding here, in the words of co-author Marcos Buckeridge, Director of the Biosciences Institute of the University of São Paulo, is that it’s “unavoidable”. It’s too late to stop average temperatures from passing this threshold “even if we were to take drastic emissions reductions measures”.

The paper “Global tree-ring analysis reveals rapid decrease in tropical tree longevity with temperature” has been published in the journal Proceedings of the National Academy of Sciences.

Tall trees in tropical forests are less vulnerable to drought

Photos from within the Amazon Rainforest in Tena, Ecuador. Credit: Jay, Flickr.

Photos from within the Amazon Rainforest in Tena, Ecuador. Credit: Jay, Flickr.

The Amazon rainforest is a huge carbon sink that, according to a 2017 study, absorbs as much carbon as all nine Amazon nations emit. Another study, however, discouragingly found that the amount of carbon the Amazon rainforest is able to absorb has declined by a third over the last decade. This decline is equivalent to over twice the UK’s annual emissions. This is partly due to the fact that the rainforest has reached a saturation point for how much carbon it can soak up, and partly due to droughts. But at least there’s some good news — according to a new study published today in Nature, taller trees in tropical forests are more resilient to droughts.

Not all trees convert solar radiation into chemical energy in the same way. Pierre Gentine, a researcher at Columbia University, New York, along with colleagues, found there is a great deal of variation in how tropical trees do photosynthesis. For instance, spatial and temporal patterns of photosynthesis in the Amazon are regulated by complex interactions between the climate, soils, nutrients and biotic factors. One other important factor that impacts photosynthesis seems to be height.

In order to understand how height affects photosynthesis in the Amazon forest, Gentine and colleagues analyzed remote sensing measurements of sun-induced fluorescence — an indicator of photosynthesis performance — as well as biophysical variables sourced from in-field and satellite measurements. The team found that taller forests are less sensitive to variations in precipitation than shorter ones.

Specifically, trees above 30 meters are three times less sensitive to drought than short trees under 20 meters. The scientists think this happens because taller trees have more extensive root systems that allow them to reach deep soil moisture during dry seasons.

However, taller forests are more vulnerable to atmospheric aridity. Leaves on tall trees constantly have a lower water content, making their photosynthesis not only more adaptable to soil drought but also more sensitive to fluctuations in atmospheric water.

The study’s results will prove useful in modeling climate change and performing conservation efforts aimed at mitigating climate change.

“[The findings] mean that the diversity in tropical forests is important to predict the response to droughts. We currently don’t represent this diversity in traits,” Gentine told ZME Science.

“We are now trying to see how forests are responding to droughts across the tropics,” he added.

212 million years ago in what is now northern New Mexico, the landscape was dry and hot with common wildfires. Early dinosaurs such as the carnivorous dinosaur in background were small and rare, whereas other reptiles such as the long-snouted phytosaurs and armored aetosaurs were quite common. Illustration: Victor Leshyk

Why there weren’t dinosaurs in the Tropics during their early history

Some 30 million years after dinosaurs emerged, they managed to rise up and dominate much of the world – then all clumped together under a supercontinent known as Pangea – except the tropics. Why dinosaurs proved so successful in higher latitudes, but failed miserably in the tropics has perplexed scientists. A possible explanation might be that during those times the tropics had an unpredictable climate, rapidly shifting from wet to dry due to a high concentration of carbon dioxide. This hypothesis is supported by a detailed analysis performed on samples collected at the Ghost Ranch in northern New Mexico, a site rich with fossils from the Late Triassic Period.

212 million years ago in what is now northern New Mexico, the landscape was dry and hot with common wildfires. Early dinosaurs such as the carnivorous dinosaur in background were small and rare, whereas other reptiles such as the long-snouted phytosaurs and armored aetosaurs were quite common. Illustration: Victor Leshyk

212 million years ago in what is now northern New Mexico, the landscape was dry and hot with common wildfires. Early dinosaurs such as the carnivorous dinosaur in background were small and rare, whereas other reptiles such as the long-snouted phytosaurs and armored aetosaurs were quite common. Illustration: Victor Leshyk

 

The first dinosaurs likely appeared on the surface of what’s today Argentina, then rapidly expanded and migrated across the world where they began to fill or dominate ecological niches. At tropical latitudes, however, this pattern was not recorded as the only fairly successful dinosaurs in the region were the small carnivorous theropods. Big, long-necked dinosaurs, or sauropodomorphs – the dominant plant eating dinosaurs commonly found higher up in latitude – could not be found in any site belonging to tropical latitude Triassic Pangaea. But who could blame them, if we’re to believe  Jessica Whiteside, lecturer at the University of Southampton, and her colleagues who found the climate of the time wasn’t at all supportive to large dinosaurs, especially the herbivores.

“Our data suggest it was not a fun place,” says study co-author Randall Irmis, curator of paleontology at the Natural History Museum of Utah and assistant professor at the University of Utah. “It was a time of climate extremes that went back and forth unpredictably and large, warm-blooded dinosaurian herbivores weren’t able to exist nearer to the equator – there was not enough dependable plant food.”

The Chinle Formation. Image: Wikipedia Commons

The Chinle Formation. Image: Wikipedia Commons

Whiteside went to Ghost Ranch, New Mexico and gathered samples from  Chinle Formation rocks, which were deposited by rivers and streams between 205 and 215 million years ago. Back then, Ghost Ranch  stood close to the equator at roughly the same latitude as present-day southern India. To reconstruct the ancient climate, the researchers gathered complementary data from fossils, charcoal left by ancient wildfires, and stable isotopes from organic matter and carbonate nodules that formed in ancient soils.

By looking at the fossilized bones, pollen grains and fern spores, the paleontologists could tell which kind of organisms roamed the region and their distribution. For instance, less than 15 percent of the animal vertebrate remains were those of dinosaurs. Instead,  reptiles known as Pseudosuchian archosaurs –  the lineage that gave rise to crocodiles and alligators – were the most abundant.  Differences in abundance of the various types of pollen and fern spores found in between the sediment layers show that there were many rapid shifts in climate.  This was confirmed by variations in wildfire burn temperature, which could be estimated by analyzing bits of charcoal recovered in the sediment layers (the amount of light reflected from the fossil charcoal under a light microscope relates directly to the burn temperature of the wood). Changes in the ratio of stable isotopes of carbon in the organic matter bookmarked times when plant productivity declined during extended droughts, but also tell us how carbon dioxide levels climbed from  1,200 parts per million at the base of the sediment section, to about 2,400 parts per million near the top. The immense volumes of CO2 are accounted to the volcanic eruptions, which were at least three times more active than today.

These continuous shifts from stable ecosystem to massive plant die-offs likely  prevented the establishment of dinosaur-dominated communities like those across South America, Europe and southern Africa, where aridity and temperatures were less extreme and humidity was consistently higher.

“The conditions would have been something similar to the arid western United States today, although there would have been trees and smaller plants near streams and rivers and forests during humid times,” says Whiteside. “The fluctuating and harsh climate with widespread wild fires meant that only small two-legged carnivorous dinosaurs, such as Coelophysis, could survive.”

The findings published in the Proceedings of the National Academy of Sciences serve as a convincing explanation for an important unsolved puzzle. Yet, they also open a window back in time to an age when the world was fundamentally different from now, climate-wise. At the same time, it’s a world that might cycle back into action with our help. Right now, the CO2 level averaged across the globe numbers over 400 parts per million or three times less the nightmarish climate of the Late Triassic Tropics.

“We show that the climatic effects of increased CO2 significantly reshaped the land plant communities that are at the foundation of terrestrial food webs,” said Whiteside.

“Our data reflect that there are possibly substantial hurdles to human sustainability in the future if we undergo the high CO2 levels predicted to occur in the coming 100-200 years,” she said.