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How do deadly microbes travel around the world so quickly?

A new study titled “Understanding atmospheric intercontinental dispersal of harmful microorganisms” paints an intriguing and concerning picture of our global atmosphere as a freeway for the international spread of deadly microbes.

Research shows that the atmosphere, particularly a region called the free troposphere, serves as an open highway for a myriad of microbes.

This natural phenomenon has serious implications for global health and requires urgent attention, as climate change and human activities such as deforestation are amplifying its impact.

This interesting study is the result of a fusion between microbiology and Earth system dynamics. It highlights the critical role of the intertropical convergence zone in this microbial traffic.

This zone, stretching both above and below the equator, is characterized by powerful warm air updrafts and the convergence of winds from both the northern and southern hemispheres.

Deadly microbes hitching a ride

The mechanism at play is quite fascinating. Intense rising winds within this region draw up vast amounts of aerosolized particles, predominantly marine, fire, and desert dust. These particles act as a vehicle for microorganisms that latch onto them and ascend into the free troposphere.

Due to their inherent characteristics and adaptive mechanisms, these microbes can travel thousands of kilometers, scattering across the globe. Their journey is facilitated by constant and long-range air currents that convene in the upper air layers and the substantial particle injection that occurs in the intertropical zone.

Climate change and human intervention, such as deforestation and the drying of large wetlands, are exacerbating this phenomenon. Increasing arid areas and desertification result in more dust and, consequently, a rise in airborne microorganisms, including pathogens.

Climate change is also altering global air currents. This allows microbes to reach places they previously could not, hence affecting the dynamics of ecosystems worldwide.

The study also offers insights into the type of microorganisms that hitch a ride on these atmospheric particles. These microbes must be able to attach and ascend, as well as endure the harsh conditions of the upper atmosphere.

What types of microbes use this sky highway?

DNA analysis reveals that while most are harmless, and some even beneficial for ecosystem dynamics, others are harmful.

Among the most detected harmful microorganisms are those that damage plants, followed by those that afflict fish, amphibians, and other animals. Last but not least, some can cause human diseases.

Allergens and antibiotic-resistant microbes have also been found among these atmospheric travelers, stressing the need for a global and systemic approach to mitigate the spread of diseases and preserve ecosystem health.

The lead author of the article, researcher Emilio O. Casamayor from the Blanes Centre for Advanced Studies (CEAB-CSIC), underscores the necessity for a global approach in his statement:

“Situations that are occurring in remote places have effects in any corner of the planet. Especially these areas in the south of the Sahara, which are judged to be of little floristic and faunal interest, should be taken care of, for the common good, because they are areas of high aerosol emission that have effects on different ecosystems that are far away”.

Three step process used by the research team

The research involved a three-step process. First, scientists collected microorganism samples from the upper layers of the atmosphere over seven years.

Next, they analyzed the DNA of the deadly microbes. Finally, they examined data provided by NASA satellites on the movement of large air masses and aerosols.

All the gathered data was then processed through biocomputation. This is a cutting-edge technological process that allows scientists to identify patterns and draw the study’s conclusions.

The AEROSMIC project, funded by the State Research Agency (AEI) and the long-term ecological monitoring network (LTER), supported this study. The project synergizes various disciplines, such as microbiology, physics, and meteorology, aiming to deepen our understanding of the long-range dispersal mechanisms of microorganisms.

More about the troposphere

The troposphere is the lowest layer of Earth’s atmosphere and contains approximately 75-80% of the atmosphere’s mass and 99% of its water vapor. It extends from the Earth’s surface to an altitude of about 8 to 15 kilometers, although this height varies with latitude and season. In general, the troposphere is higher at the equator and lower at the poles.

The word “troposphere” is derived from the Greek word “tropos,” meaning “turning” or “change.” This is apt, as it reflects the fact that this layer of the atmosphere is a dynamic and active region, experiencing a lot of turbulent mixing and weather phenomena.

The weather conditions we experience daily occur in the troposphere. This includes the movement of air masses, the formation and dissipation of clouds, and various weather events such as rain, snow, storms, and tornadoes. This layer is also where the majority of the Earth’s biological life is found.

Conditions in the troposphere

Temperature in the troposphere decreases with altitude, with the warmest temperatures found at ground level and cooling as you ascend. This trend is due to the heating of the Earth’s surface by the Sun, which in turn warms the air close to the surface.

This decrease in temperature with height is known as the environmental lapse rate, which averages about 6.5°C per kilometer (about 3.6°F per 1,000 feet) of altitude.

The troposphere is bounded above by the tropopause, a boundary marked by the cessation of decreasing temperature with increasing height. Above the tropopause lies the stratosphere, the second layer of the Earth’s atmosphere.

While the troposphere is generally a well-mixed region due to turbulent air currents, it can still harbor pollution, such as smog near the ground. Also, as we learned above, it transports deadly microbes around the world.

Also, it is within the troposphere that we see the effects of climate change, including global warming, which is driven by the increased concentration of greenhouse gases such as carbon dioxide and methane.

Conclusively, while it’s the thinnest of all the atmospheric layers, the troposphere is vitally important to life on Earth. It’s where weather happens, where planes fly, and it provides the air we breathe. Understanding it is key to understanding many aspects of Earth’s climate system.

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