The Tropical Rainforest is renowned for its immense diversity of plant and animal species. Moreover, as an ecosystem, it serves essential functions such as local water storage. This has direct effects on the water cycle in specific regions, like the southern parts of Brazil, Paraguay, central eastern Argentina, and Uruguay, which are closely connected to the water cycle of the Amazon. The rainfall in these areas heavily depends on the precipitation in the Amazon region.
Additionally, Tropical Rainforests significantly contribute to stabilizing the global climate.
They play a crucial role in sequestering large amounts of carbon dioxide (CO2) from the air. Through the process of photosynthesis, they absorb CO2 and use carbon for their growth while releasing oxygen, which is essential for human life. Photosynthesis is a fundamental function of plants and one of the most important chemical processes on Earth, contributing significantly to sustaining life.
Forests act as CO2 sinks when they store more greenhouse gas through tree growth than is released by decaying trees.
Why the natural ability of Tropical Rainforests to mitigate CO2 emissions is at risk:
In the 1990s, intact rainforests could absorb and reduce about 17 percent of human-made CO2 emissions. However, recent calculations show that this value has now decreased to about six percent. Researchers attribute this to the fact that the proportion of intact rainforests has decreased by almost one-fifth, while global CO2 emissions have increased by almost half. This decline in intact rainforests contributes to a reduction in their ability to effectively capture CO2 and mitigate climate change.
If the current trend continues, rainforests could transition from being CO2 sinks to CO2 emitters within the next 15 years. This concerning finding is based on an extensive analysis where scientists studied 300,000 trees in the Amazon and African rainforests over several decades.
In general, additional CO2 can stimulate plant growth. Through the process of photosynthesis, plants use carbon dioxide with the help of the green pigment chlorophyll, sunlight, and water to produce sugar, which is essential for plant cell growth.
However, this fertilization effect is increasingly undermined by negative influences, such as rising temperatures and drought, which slow down growth or even lead to the death of trees.
In the 1990s, tropical rainforests could absorb about 46 billion tons of CO2 from the atmosphere. In comparison, in the 2010s, it was only about 25 billion tons. According to researchers, this decrease is equivalent to the CO2 emissions from fossil fuels emitted by Germany, France, the United Kingdom, and Canada combined over a decade. This alarming discrepancy illustrates the decline in the ability of tropical rainforests to capture CO2 and mitigate climate change. The loss of intact rainforest areas and increasing CO2 emissions contribute to this concerning trend. It becomes clear that protecting and restoring tropical rainforests play a crucial role in addressing the climate crisis.
For their analysis, the researchers examined 244 forest areas in eleven countries in the Congo Basin and Central Africa. Between 1968 and 2015, they recorded all trees within the test areas with a stem diameter of more than ten centimeters. To assess tree growth, they returned every few years, remeasured the stems, and documented tree mortality. The results were compared with data from 321 additional test areas in the Amazon rainforest. Based on this data, an estimate was made of how much carbon dioxide was stored in the forests. The study revealed that the carbon sink of the Amazon rainforest has been losing its effectiveness since the mid-1990s. In the African rainforests, this effect was observed only from the year 2010 onwards. The researchers attribute this to the fact that the Amazon rainforest is now more frequently exposed to droughts, which negatively affect its growth and carbon storage.
In addition, trees in the Amazon region grow faster on average and also die faster. This means they store CO2 for a shorter period of time. The impacts of climate change could therefore be noticed more quickly in the Amazon region. However, the potential role of nutrient availability was not investigated by the researchers in this study. It remains an open question whether this could be an additional factor influencing tree growth and carbon storage. Further research could help better understand these relationships.
If the current trend continues, there is a possibility that the CO2 storage capacity of the rainforests could decrease by another 14 percent by the year 2040. In the Amazon region, this loss could lead to a complete loss of CO2 storage capacity as early as 2035. From that point onwards, the dying trees would emit more greenhouse gases than could be absorbed by new trees. This development would have serious implications for the global carbon balance and climate change.
While such predictions may have some uncertainties, they still illustrate the concerning direction we are heading. They serve as a warning and highlight the potentially dangerous consequences if certain trends persist. It is important to take such forecasts seriously and take appropriate actions to reverse or mitigate negative developments. Through targeted conservation measures and efforts to combat climate change, we can attempt to halt the negative impacts and create a more sustainable future.
What is the Earth’s albedo, and how does it change through the destruction of the tropical rainforest?
Albedo refers to how much light or sunlight is reflected by a surface that doesn’t act as a mirror. Another word for albedo is „reflectivity.“ The Albedo Effect describes the reflection of sunlight and is very important in climate research.
The reflectivity represents the portion of sunlight that gets reflected by the surface. When solar radiation hits a surface, some of it gets absorbed, meaning that part is taken in by the surface and converted into energy, for example. The other part of solar radiation gets reflected, which means it gets sent back into the atmosphere.
The higher the portion of reflected radiation is, the higher the reflectivity, and consequently, the higher the albedo.
Albedo is expressed as a number from 0 to 1, where 0 means the object doesn’t reflect any light at all, and 1 means the object reflects all the incoming light. Albedo can also be expressed as a percentage from 0 to 100%.
Albedo of the earth
The average albedo of our planet is 0.3. This means that about 30% of the incoming sunlight is reflected by the Earth’s surface and sent back into space. However, the albedo can vary depending on the surface. Here is a table showing the average albedo of different surfaces:
| Surface | Albedo Range |
|---|---|
| Fresh Snow | 75-95% |
| Deep Water (low sun angle) | 80% |
| Clouds | 60-90% |
| Dune Sand | 30-60% |
| Bare Soil, Fallow | 7-17% |
| Tropical Rainforest | 10-12% |
| Deciduous Forest | 15-20% |
| Coniferous Forest | 5-12% |
| Grasslands, Meadows | 12-30% |
| Agricultural Crops | 15-25% |
| Urban Areas | 15-20% |
| Deep Water (high sun angle) | 3-10% |
Albedo of the clouds
The presence of clouds on our planet has a significant impact on the albedo. Compared to a cloudless sky, clouds reflect more light back into space. However, the albedo of clouds can vary depending on different factors, such as their height, size, and the number and size of water droplets they contain. These characteristics determine how effectively clouds can reflect the incoming sunlight. Overall, clouds help reduce the absorption of solar radiation by the Earth’s surface, contributing to the planet’s cooling. (The albedo of clouds varies between 30 and 90%).
The color of clouds varies from bright white to dark gray due to the scattering of light by the water droplets they contain. Larger droplets have a larger surface area and therefore reflect more light than many smaller droplets. If we are under a large cumulonimbus cloud with large droplets, the surroundings appear dark because only a little light passes through the cloud. However, viewed from space, the same cloud would appear very bright white because it actually has a high albedo and reflects a lot of sunlight. In contrast, cirrus clouds are almost transparent. From space, they would appear grayer because their albedo is lower, and they reflect less light.
Deforestation of the tropical rainforest changes the Earth’s surface albedo, which in turn affects air and ocean currents as well as rainfall patterns. Deforestation contributes to changes in global weather patterns and an increase in extreme weather events. A NASA study shows that deforestation in the Amazon region will particularly impact the Gulf of Mexico, Texas, and Northern Mexico.
The destruction of the rainforest has negative effects on the water balance and climate of surrounding areas. Deforestation leads to soil drying. At the same time, forest clearance results in changes in regional rainfall patterns and a rise in temperatures. It is expected that during the rainy season, rainfall amounts will increase, causing strong erosion, while the Amazon basin will suffer from severe droughts during the dry season. This, in turn, significantly affects the frequency of forest fires.
Unique peat swamp forests are under threat and disappearing. These forests are characterized by their soils consisting of layers of peat bog several meters thick. These peat layers have formed over thousands of years and store enormous amounts of carbon dioxide (CO2). Deforestation and burning of these forests release the stored CO2, contributing to the greenhouse effect.