Tag Archives: rainforest

Amazon Rainforest Faces Drought as Deforestation Disrupts Atmospheric Rivers

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Deforestation in the Amazon

Vast areas of the Amazon rainforest are cleared for cattle ranching

Michael Dantas/AFP via Getty Images

The alarming rate of deforestation is significantly diminishing rainfall patterns across the Amazon, indicating that this vital rainforest could hit a catastrophic tipping point sooner than previously anticipated.

Research from 1980 to 2019 indicates that rainfall in the southern Amazon basin has diminished by 8 to 11 percent, based on satellite data and rain gauge readings. During this same time frame, tree cover in the region has shrunk by 16 percent, primarily due to deforestation linked to beef cattle ranching.

Contrastingly, deforestation has been less pronounced in the northern Amazon Basin, where precipitation has only shown minor increases that lack statistical significance.

Recent research highlights that deforestation contributes to arid conditions within a 300-kilometer radius. This new analysis reveals that this effect spans over a basin wider than 3,000 kilometers, suggesting that deforestation harms not just forests, but also the productivity of adjacent ranches and soybean farms, according to Dominique Spracklen from the University of Leeds.

“Some in agribusiness may perceive sections of the forest as underutilized land. Yet, these forests play a crucial role in maintaining regional rainfall, which in turn benefits our agricultural practices,” Spracklen explains.

Global warming is exacerbating the drying of the Amazon, culminating in extreme droughts and unprecedented wildfires in 2024. However, atmospheric studies led by Spracklen and colleagues indicate that deforestation is responsible for 52 to 75 percent of the decline in rainfall.

Moisture from the Atlantic Ocean is transported by prevailing winds into the Amazon, where it precipitates as rain. Plants contribute to this cycle as evaporation and transpiration return about three-quarters of that water to the atmosphere. Further downwind, it falls again as rain through multiple cycles, creating “flying rivers” that distribute moisture across the rainforest.

When forested areas are destroyed, over half of the rainwater is redirected to rivers and subsequently returns to the ocean, depleting the moisture available for the flying rivers and leading to reduced rainfall. Additionally, this diminishes atmospheric instability necessary for storm cloud formation, Spracklen and his team discovered.

As fewer trees slow down the wind, it tends to pick up speed, removing more moisture from the area.

Unlike previous research, this study employs a combination of data and modeling to effectively illustrate how deforestation impacts rainfall patterns, asserts Yadvinder Malhi from Oxford University.

“The atmosphere becomes smoother and, in a sense, slipperier. There’s reduced friction with the ground, enabling moisture to travel further out of forested regions,” Malhi notes, emphasizing the significance of secondary atmospheric processes often overlooked in prior studies.

Scientists voice concerns that the cumulative impact of heightened temperatures, drought, and deforestation could push the Amazon rainforest to a tipping point where it transitions into a savannah ecosystem, although the timeline for this transition remains uncertain. Spracklen and his colleagues found that climate models may underestimate the influence of deforestation on rainfall by as much as 50 percent, implying that the rainforest could face significant threats earlier than anticipated.

According to a 2022 study, there is a 37% probability that certain regions of the Amazon could vanish by 2100 if global temperatures, currently at 1.4°C, rise to 1.5°C. However, this does not necessarily imply that rainforests will convert into savannahs; it may lead to the emergence of fewer species and scrub forests capable of storing less carbon.

“The Amazon’s sensitivity is greater than we previously imagined, which is troubling,” he states. “We may be closer to the deforestation threshold than we realize, although there remains significant uncertainty surrounding this issue.”

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Source: www.newscientist.com

Climate Change is Encouraging Tree Growth in the Amazon Rainforest

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The average size of trees in the Amazon Rainforest is gradually increasing as carbon dioxide levels rise. This means that these larger trees play a crucial role in determining whether the forest acts as a carbon sink.

How forests adapt to changing climates remains a significant question. One theory suggests that larger trees are more vulnerable to reductions as they face challenges from climate-related phenomena, such as droughts and high winds. Understanding how forests respond to these changes is crucial for future climate models.2 It’s essential to address atmospheric issues to mitigate global warming.

Adriane Esquivel-Muelbert from Cambridge University and her team at the Rainfor Amazon Forest Inventory Network have measured tree diameters in 188 plots averaging 12,000 square meters across the Amazon Basin. The monitoring period varied, with some plots observed for around 30 years. Meanwhile, 2 atmospheric concentrations are reaching near record levels.

“We monitor certain areas in the forest where the average tree size has increased over time. This indicates that these trees are capable of storing more carbon than they did in the past,” researchers noted, highlighting an average diameter increase of about 3.3% every decade.

“The structural composition of the Amazon forest is continually changing throughout the basin,” says team member Rebecca Bunberry Morgan from the University of Bristol, UK. “There are more sizable trees and fewer smaller ones, indicating a shift in average size towards larger trees.”

She adds that the average diameter of trees in mature, undisturbed forest areas remains relatively constant as they replace and grow larger trees where seedlings have fallen. Researchers believe that Amazon trees are responding positively to the increasing atmospheric 2 levels, resulting in enhanced growth and biomass accumulation. “Larger trees tend to thrive as they compete more effectively for light and water,” remarks Esquivel-Muelbert.

This implies that large trees are disproportionately vital for the carbon storage capacity of the forest, meaning their loss would have significantly adverse effects, she concludes.

“A key finding is that 2 wood serves as a globally significant carbon sink, functioning as a fertilizer that promotes tree growth while being influenced by many factors.” Peter Etchells at Durham University, UK, states, “However, this could change as climate continues to evolve, potentially impacting the balance of growth, nutrient availability, temperature, and CO.2?”

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  • Amazon rainforest

Source: www.newscientist.com

The Sahara Desert and Amazon Rainforest may have been the first habitats for dinosaur evolution

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If dinosaurs really did appear near the equator, life would have been particularly hot and dry.

Mark Whitton/Natural History Museum Trustees

Dinosaurs may have first evolved near the equator, rather than far south in the Southern Hemisphere as previously thought. Modeling studies suggest they originated in areas covering what is now the Amazon rainforest, the Congo Basin, and the Sahara Desert.

“Given the gaps in the fossil record and the evolutionary tree of dinosaurs, it is very likely that this is the central point of dinosaur origin,” he says. Joel Heath At University College London.

Dinosaurs evolved during the Triassic period, which lasted from 252 million to 201 million years ago, but there is “considerable” uncertainty about when and where they evolved, Heath said. The oldest known fossils of these animals are about 230 million years old, but there are enough features to suggest that dinosaurs have already been around for millions of years. “There must have been a lot going on in terms of dinosaur evolution, but we don't have the fossils,” he says.

At this time, the Earth looked very different. All the continents were combined into a single supercontinent called Pangea, shaped like a C with its center straddling the equator. South America and Africa were located in this southern hemisphere part and were fitted together like pieces of a jigsaw puzzle. The earliest known dinosaurs lived in the southern parts of these two continents, in present-day Argentina and Zimbabwe, where dinosaurs were thought to have originated.

To learn more, Heath and his colleagues built a computer model that works backwards in time from the oldest known dinosaurs to the group's origins. They considered uncertainties such as gaps in the fossil record, possible geographic barriers, and ongoing questions about how the earliest dinosaurs were related to each other to create dozens of versions. has been created.

Most of these simulations concluded that dinosaurs first appeared near the equator, with only a few supporting a southern origin.

Paleontologists have tended to believe that dinosaurs couldn't have originated near the equator, Heath said. One reason for this is that no early dinosaur fossils have been found in the area. Moreover, it was a difficult place to live. “It was very, very dry and very hot,” he says. “It is believed that dinosaurs could not have survived in such conditions.”

However, most models do not. “This suggests something that we didn't really think was possible until now,” Heath says.

In fact, there may be a more prosaic explanation for the lack of early dinosaur fossils found near the equator. Paleontologists tend to conduct excavations in North America, Europe, and more recently China. “There are many areas of the planet that are completely ignored,” says Heath. He added that geologists have not found many rocks of suitable age in the area associated with the findings that can be excavated. “It may not be exposed in a way that we can easily investigate.”

But evidence supporting Heath's idea has recently come to light. On January 8th, researchers david loveless At the University of Wisconsin-Madison, oldest known dinosaur Originally from northern Pangea. They discovered what they call a species new to science. Avaitum Banduiche, sauropodomorphs related to long-necked dinosaurs such as diplodocus That evolved later. The research team discovered the 230-million-year-old rock in Wyoming's Popo Aggie Formation.

If dinosaurs were already present north and south of Pangea that long ago, there's no way the middle of the equator would be closed off to them, Heath said. “They must have been crossing the area.”

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Source: www.newscientist.com

Fossil of giant freshwater turtle discovered in the Amazon rainforest of Brazil

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Pertocephalus maturin Its shell length probably reaches about 1.8 meters (5.9 ft), making it one of the largest freshwater turtles ever discovered. The discovery marks the latest known occurrence of giant freshwater turtles and suggests coexistence with early humans in the Amazon.

rebuilding the life of Pertocephalus maturin. Image credit: Júlia d’Oliveira.

The newly discovered turtle species lived in what is now Brazil during the late Pleistocene, between 40,000 and 9,000 years ago.

named Pertocephalus maturinthe ancient animal may have reached a carapace length of about 1.8 meters.

Dr. Gabriel Ferreira, a paleontologist at the Senckenberg Center, said: “Freshwater turtles, in contrast to their terrestrial and marine relatives, rarely have such gigantic morphologies and are the only known species to date. “This is very surprising since the youngest giant fossils come from Miocene deposits.” Human Evolution and Paleoenvironment at the University of Tübingen.

“The carapace is up to 1.4 meters (4.6 feet) long; Asian narrow soft-shelled turtle (chitra chitra) The length is approximately 1.1 m (3.6 ft). South American river turtle (Podocnemis Expansa) They are some of the largest freshwater turtles alive today. ”

“In the past, only a few freshwater turtles with carapace lengths exceeding 1.5 meters (4.9 feet) were known,” he added.

“Such megafauna are most recently known, mainly from the Miocene period, about 23 million to 5 million years ago.”

huge partial lower jaw Pertocephalus maturin It comes from the Rio Madeira layer.

This specimen was collected by gold miners at a site known as the Taclas Quarry in Porto Velho in the Brazilian Amazon.

Morphological and phylogenetic analyzes of this fossil revealed close kinship with modern Amazonian species and suggested an omnivorous diet.

“Pertocephalus maturin “This is the youngest known giant freshwater turtle and suggests coexistence between this ancient species and early human residents of the Amazon region,” the paleontologists said.

“People settled in the Amazon region about 12,600 years ago. We also know that large turtles have been a food source for humans since the Paleolithic period.”

“Freshwater turtles are much more difficult to catch because of their agility, but we wonder if early humans also ate them.” Pertocephalus maturin It is not yet clear whether they fell victim to human expansion along with South American megafauna. ”

“Here we need further data from late Pleistocene and early Holocene deposits in the Amazon basin,” Dr. Ferreira said.

discovery of Pertocephalus maturin is reported in paper in a diary biology letters.

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GS Ferreira other. 2024.Latest freshwater giants: new Peltocephalus (Pleurodira: Podocnemididae) A late Pleistocene turtle of the Brazilian Amazon. Biol.Let 20(3):20240010; doi: 10.1098/rsbl.2024.0010

Source: www.sci.news

By 2050, Half of the Amazon Rainforest May be Reaching a Climate Tipping Point

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Forest fires in the Amazon in October 2023

Gustavo Basso/Null Photography via Getty Images

Large parts of the Amazon rainforest are threatened by the combined effects of drought, heat and deforestation, and some ecosystems may be pushed past tipping points. But the likelihood of a larger collapse remains uncertain.

“Forests as a whole are very resilient, so we still have room to act,” he says. Marina Hirota at the Federal University of Santa Catarina, Brazil.

Researchers have warned for decades that rising temperatures and deforestation could push the Amazon past a tipping point, leading to runaway feedbacks that could lead to a rapid transition from forest to savannah. The drought and heat caused by the ongoing El Niño phenomenon, as well as the warming temperatures caused by climate change, are once again on the rise.

But climate and ecological models that describe the Amazon's highly complex structure disagree on when and where such a tipping point would occur.

To understand which regions of the Amazon are most at risk, Hirota and his colleagues looked at satellite data to see how several different ecosystem stressors might change in the coming decades. evaluated. These include dry season temperatures, exposure to drought, and the risk of fire and deforestation.

They estimate that 10 percent of the Amazon basin is at risk of being exposed to at least two of these stressors by 2050 and is therefore likely to transition to degraded forest- or savanna-like ecosystems. I discovered that. 47% of this watershed is predicted to be exposed to at least one stressor, meaning it is also exposed to some hazard.

“Due to ongoing changes, we will lose some forest, but there are things we can do to prevent it from reaching 47%,” Hirota says. She said the majority of forests that are not exposed to stressors are located within protected areas; indigenous territory, which is associated with low deforestation rates. Brazil's deforestation rate also fell sharply under President Luiz Inacio Lula da Silva's administration. Increased in other areas as well Amazon's.

dominique spracklen Researchers from the University of Leeds in the UK say the study is a powerful investigation into the range of threats facing the Amazon. But he says the discrepancies between models predicting potential tipping points remain unresolved.

For example, models predict that some of the negative effects of warming could be offset by increased concentrations of CO2 in the atmosphere, which could boost plant growth. . However, other factors such as nutrients and water availability vary widely across the basin and influence the strength of this impact, creating considerable uncertainty in modeling the future of the Amazon. .

“It's a very scary place for such an important ecosystem,” he says.

Nature
DOI: https://doi.org/10.1038/s41586-023-06970-0

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Source: www.newscientist.com