The technique of mapping genetic material allows the discovery of countless pieces of evidence about the past and future. Regarding humans, it is possible to understand the inheritance contained in genes, coming from relatives of ancient generations and even predict diseases. This possibility holds true for other animals too. By observing the genome of a typical species from the Amazon, birds of the genus Willisornis, better known as Common Scale-backed Antbird or “spotted”  [rendadinhos], researchers were able to identify natural facts that affected the biome thousands of years ago: climate changes were present, leading the forest to drought and promoting changes in vegetation cover, affecting local communities.

This was the first time that the result was reached by means of the study of the species' DNA. The research, carried out over six years and led by the Instituto Tecnológico Vale – Desenvolvimento Sustentável (ITV-DS) [Vale Technological Institute – Sustainable Development], with the participation of the Laboratório Nacional de Computação Científica [National Scientific Computing Laboratory] in Rio de Janeiro, the Federal University of Paraíba (UFPB), Federal University of Pará (UFPA) and the University of Toronto, in Canada, chose to investigate the Common Scale-backed Antbirds because they are considered natural bioindicators of the forest, that is, they occur solely in this environment and are able to record information about the distribution of vegetation cover over time in the genome.

Time capsules

Nine individuals had their genome sequenced during the study. With the collected data, it was possible to understand the impacts that climate changes in the Amazon during a certain period of time in history had on birds – population size, more intense relationships between relatives and lower genetic diversity were some of the factors found in the DNA. 

Because the Common Scale-backed Antbirds are also considered by researchers as “time capsules”, what happened in the forest in past times was used within the scope of the analyzes to understand the dynamics predicted for the future of the biome as well as when the changes occurred and what magnitude and impact they had.

Alexandre Aleixo, environmental genomics investigator at ITV and lead researcher of the study that sequenced the birds' genetic material, explains that some points have already been well defined throughout the research. The decrease in populations of species associated with the forest in a period ranging from 80 thousand years to 20 thousand years ago is one of the prominent findings from what was possible to read in the marks left in the DNA of the Common Scale-backed Antbirds. “This was the period called Glacial (Ice age) and culminated in the reduction of the Amazon Forest by approximately 60% considering its size today. This was felt by forest species.”

Southeast

In addition to the population decline identified, studies have also shown that the southeastern Amazon was proportionally more affected by climate change at the time than other regions. The impact prediction models which map the new consequences of the constant increase in the planet's average temperature also indicate that this part of the biome will be predominantly affected. “So, history recaps the past and precisely with the conviction that this really happens to the species, we want to understand what caused them to survive, even in the face of a very hostile scenario for their presence in the southeast”, emphasizes the researcher.

Ice age preserves climate changes that occurred in the Amazon

That climate change brings consequences to the Amazon is not a new evidence. For distinct reasons, the phenomenon occurred during the so-called Ice Age, a period in which the planet's temperature was 7.8°C below zero according to a study published in the journal Nature. For comparison purposes, the rate in the last century was 14°C. Currently, industrial processes and the burning of fossil fuels are responsible for the changes, but Alexandre Aleixo highlights that in the past other causes were involved. “Perhaps, the main cause in the past was what they called changes related to the Earth’s orbit,” says the researcher.

“So, these changes are cyclical and actually lead to situations in which the sun's rays reach the Earth more or less intensely. In glacial periods, when the ice increases and the Amazon has more drought, you have a decrease in solar radiation reaching the Earth, this is what explains it. In other words, current climate changes, which are, in fact, mainly related to the increase in CO2 [carbon dioxide], are a very different scenario from what caused those climate changes and the drying out of the Amazon 20 thousand years ago . The causes are different, however, apparently as far as we can understand, the effects were very similar”, says Aleixo.

Future

Identifying climate changes that have taken place over the years and establishing how they have affected the biodiversity of the Amazon was one of the research focuses. The other is to help develop measures to minimize the spread of such effects throughout the biome. “One of the main actions underway is precisely [to understand] how to keep the reserves, which have already been delimited, intact. It is kind of intuitive, we think that once the reserve has been delimited, it will be safe. But climate change has shown that this is not the case. Even if a reserve is well preserved, well monitored, climate change will alter flora and fauna”, warns Aleixo.

In the case of the Common Scale-backed Antbird, a species that survived climatic changes of the ice age, the investigation starts in search of the conditions that led to this scenario of resistance and birds’ survival. According to the results, affirms the researcher, reintroductions to the biome can be made. “Also, by way of ecological corridors facilitating dispersal, the movement of these species, towards conservation units that will be greatly affected by climate change. Then, it is a form of management, as long as you know how the genome responds to climate change and identify which populations are more resistant”. Explains the scientist.

Climate change impacts the migratory flow of Birds

Studies led by ITV showed that the biodiversity of Common Scale-backed Antbird from the Amazon was affected by climate changes of Ice Age. Nowadays, another problem becomes obvious: species that migrate to the biome are threatened and may risk losing a safe environment for their stay. Marcos Pérsio, professor and coordinator of the Laboratório de Biogeografia da Conservação e Macroecologia (Biomacro-Lab) [Laboratory of Biogeography of Conservation and Macroecology] at the Federal University of Pará (UFPA), emphasizes that the birds that migrate to the region are in search of better climatic conditions and food resources. 

Usually, the species that migrate to the Amazon reproduce. It means to say that they live in both the Northern Hemisphere – the United States and Canada – and the Southern Hemisphere – Argentina and Southern Brazil. They are small birds that spend an average of three months away from their natural habitat and then return for a new breeding season. Pérsio affirms that the number of species performing this annual journey varies from 30 to 40 and that they spend the season in the Amazon rainforest because of the great variety of environment types and foods. “In the Amazon rainforest, temperature is basically the same all year long, in other words, a stable, warm temperature and plenty of food, both insects and fruit”

Risks

However, this migratory flow is at risk due to climate change and its consequences to the Amazon biome. According to the professor, the lack of rainfall, the resulting droughts as well as the food offer - insects and fruit – which is beginning to be directly affected, causes the alteration of hydrological cycles . “When it starts to change the climate, it starts to change the periods of greater abundance of food. When these birds leave the United States in September and August to reach the Amazon in October, they expect to find a large supply of food. The problem is that these climate changes can cause changes to the food supply”.

Projections point to a worrying future

This climate changes reality may even interfere with the forest's internal processes, as native and migratory species begin to compete in search of food. The result,  emphasizes Marcos Pérsio, is the individuals’ death. In addition to this, a 2024 study conducted by the UFPA researcher also identifies that climate change is a problem that goes beyond this fact. 

“We have examined 43 species threatened with extinction living in the Amazon, and we made projections of how climate change could impact the geographical distribution of these species. What we have found it is quite worrying”.

Future

“If we think about an optimistic scenario, in which environmental legislation will be respected, new conservations units will be created, even so, 65% of these 43 species will suffer a sharp reduction in their living areas, in other words, they will lose, on average, more than 80 % of their occurrence area.  It is a meaningful reduction. In a pessimistic scenario, 96% of these species will have an even greater reduction in their geographic distribution. Basically, 84% of these taxa simply will not have any suitable areas in the future and will be at serious risk of becoming extinct within a few decades”, says Pérsio.

Learn more

- The Common Scale-backed Antbird is a Passeriforme of the Thamnophilidae family. 

- Its scientific name means: Willis = a tribute to the Dr. Edwin O’neil Willis – (1935 - 2015), North American Professor and ornithologist who lived in Brazil; and ornis (from the Greek) = bird; and poikilonotos (from the Greek)= stained, laced. ⇒  Laced bird of Willis.  

- It has about 13cm long and weighs 17g. The male is generally grey, with a black tail and wings. It exhibits white stripes in the back, white bars on its wings and white spots at the tip and base of its tail. The females show ochraceous head and chest, grey chest and light grey neck.    

- In general, these birds live in pairs, in vertical perches close to the ground, which they quickly reach just to grab their prey (small insects and spiders). They catch insects in the foliage nearby. They frequently search for Army-ants.

- It is a common species in humid forest undergrowth. It is less frequent in floodplains.  

SOURCE: https://www.wikiaves.com.br/wiki/rendadinho