PART TWO

The Amazon: what actually kills the rainforest?

By Günter Försterra & Vreni Häussermann

While in the first part we focused on the importance of the Amazon rainforest and what consequences its degradation does and will have, in this second part we want to explain the actual threats that lead to loss and degradation of the rainforest.

Extent of Deforestation

In the first part we explained that between 17 and 20% of the original forest surface has already been lost and another 14-17% is heavily degraded (1).

Trends in Deforestation

These losses are mainly due to direct and intentional deforestation, either by logging or by fire clearing. After a peak in deforestation in 2004 with 27.000km2/year (only surpassed by 28.000km2 in 1995) the deforestation rate dropped to 4000km2 in 2012, which is still the area of the Hawaii main island. But from thereon it rose again continuously and is now at approximately 10.000km2 of forest surface loss every year again (2). That is the size of Sicily every year!

Drivers of Deforestation

The reason for logging is the interest in valuable timber. Although in relation to other methods for removing forest logging is less efficient and logging for timber only contributes 10-15% directly to the loss of tropical forests, logging roads that often penetrate deep into the primary forest are the main entrances through which other forest damaging activities enter the area. A study by a Brazilian commission showed that 80% of all logging in the Amazon was illegal during the late 90’s (3). Along logging roads illegal gold digger, farmers and hunters conquer the area and contribute to degradation and destruction of the rainforest.

Drivers of Deforestation

The reason for logging is the interest in valuable timber. Although in relation to other methods for removing forest logging is less efficient and logging for timber only contributes 10-15% directly to the loss of tropical forests, logging roads that often penetrate deep into the primary forest are the main entrances through which other forest damaging activities enter the area. A study by a Brazilian commission showed that 80% of all logging in the Amazon was illegal during the late 90’s (3). Along logging roads illegal gold digger, farmers and hunters conquer the area and contribute to degradation and destruction of the rainforest.

Fire Clearing for Agriculture

When the timber is not in focus and larger areas are to be cleared in a cheap and fast way, fire clearing is the most applied method to remove the forest. Some areas are cleared this way for mining (2% direct plus 9% indirect), oil drilling and settlements but the main reason why forest is burned down is for agriculture (70%) (4).

Since the tropical soils generally are poor in nutrients and have limited abilities to store nutrients, the ash from the burned trees has only a short-term fertilization effect that fades rapidly, and often in the second or third year when the yield drops the farmers move on and new areas are burned down (5). But more than small-scale farmers, large agricultural companies, some of them multinational, burn down rainforest either for large monocultures of soybeans and sugar cane or for creating grass land for cattle or they take over areas that have been burned down and abandoned by small farmers. This method although officially banned has become more popular again under President Bolsonaro who weakened environmental legislation, demounted the agencies that oversaw enforcing the environmental laws and combating forest fires in the Amazon and encouraged the farmers with his rhetoric to proceed with their practices. A typical succession is roads, timber, fire, crop, cattle, soybeans.

 It’s not only Brazil

But the fact that roughly two thirds of the Amazon rainforest is within Brazilian borders (6), often draws the focus away from other countries where the situation may even be worse. In Bolivia e.g. the government under Evo Morales allowed in 2019 forest clearing in two provinces in favor of cattle farming for the Chinese market. The fires got out of control and destroyed almost 10.000 km2 of forest. During the second half of 2023, another 3.000 km2 of forest has already burned down when the dry season in Bolivia had not even really started. Consequently, relative to its share on the Amazon the loss of primary forest in Bolivia is disproportionately high in comparison to other Amazon countries (7).

 It’s not only Brazil

But the fact that roughly two thirds of the Amazon rainforest is within Brazilian borders (6), often draws the focus away from other countries where the situation may even be worse. In Bolivia e.g. the government under Evo Morales allowed in 2019 forest clearing in two provinces in favor of cattle farming for the Chinese market. The fires got out of control and destroyed almost 10.000 km2 of forest. During the second half of 2023, another 3.000 km2 of forest has already burned down when the dry season in Bolivia had not even really started. Consequently, relative to its share on the Amazon the loss of primary forest in Bolivia is disproportionately high in comparison to other Amazon countries (7).

Impact of Fires on species distribution

While in the past most of the fire-clearing was intentional, in drier and degraded forests and especially during dry periods like in 2019 many of these fires get out of control and spread far beyond the intended limits. In 2019 alone there were 76.000 different forest fires registered for the Amazon region (8). The more a rain forest dries out, the easier it burns and the less it can recover. A vicious circle that gained speed during the last decade. The impacts of fire on the distribution ranges of species in Amazonia could be as high as 64%, and greater impacts are typically associated with species that have restricted ranges (9).

Impact of El Niño and Global Warming

To a certain extent, dry periods are a natural phenomenon in the Amazon, especially during El Niño events. But El Niño is becoming more frequent and more severe due to global warming (10,11). As we explained in the last part, the damaged Amazon has already turned from being a carbon sink into a CO2 and methane emitting area, which contributes to global warming (12,13,14) – another feedback loop. But in addition to this, the humidity that is evaporated from the forest itself and the forest’s capacity to retain water has already weakened, which enforces droughts (15). This southern hemispheric summer’s drought in the Amazon basin is the most severe since the beginning of the recordings (16). Again, we are in the early phase of a vicious circle where a damaged ecosystem has less resilience against disturbance, which enhances the frequency and the magnitude of the disturbance.

Impact of El Niño and Global Warming

To a certain extent, dry periods are a natural phenomenon in the Amazon, especially during El Niño events. But El Niño is becoming more frequent and more severe due to global warming (10,11). As we explained in the last part, the damaged Amazon has already turned from being a carbon sink into a CO2 and methane emitting area, which contributes to global warming (12,13,14) – another feedback loop. But in addition to this, the humidity that is evaporated from the forest itself and the forest’s capacity to retain water has already weakened, which enforces droughts (15). This southern hemispheric summer’s drought in the Amazon basin is the most severe since the beginning of the recordings (16). Again, we are in the early phase of a vicious circle where a damaged ecosystem has less resilience against disturbance, which enhances the frequency and the magnitude of the disturbance.

Everything is connected

If all this would not be enough, there is another sword of Damocles hanging over the Amazon rainforest. Glaciologists and climatologists are very worried about the condition of the Greenland ice shield. Due to Global Warming it is shrinking faster than originally predicted and its shrinkage could gain in speed through several feedback loops (17,18). The fresh water released from this ice melting reduces the salinity of the northwestern Atlantic surface water which weakens one of the largest oceanic pumps on the globe, the thermohaline circulation (19,20). Consequently, the Atlantic meridional overturning circulation (AMOC) with the Gulf Stream and the North Atlantic Drift could slow down, which would shift the Intertropical Convergence Zone (ITCZ) or also called monsoon trough. Studies of Greenland ice cores showed that this has happened several times since the Würm Glaciation and that it can happen in a surprisingly short time. The Amazon area would receive significantly less rain, which adds to the other factors that already enhance drought in the area (21).

Impact of Global Warming and Feedback Loops

But even without the feedback loop from AMOC-ITCZ system, global warming puts the Amazon in danger. A 2009 study found that a 4 °C rise (above pre-industrial levels) in global temperatures by 2100 would kill 85% of the Amazon rainforest while a temperature rise of 3 °C would kill some 75% (22). Another feedback loop where global warming damages the Amazon and a damaged Amazon enhances global warming.

The Amazon is at a dangerous tipping point where further degradation could trigger and enhance several climatic feedback loops. Action is required NOW!

References

  1. World Wildlife Fund (downloaded December 2023): What animals live in the Amazon? 
  2. Mongabay (2020, January 15): For final months of 2019, Amazon deforestation hits highest level in at least 13 years.
  3. Viana, G. 1998. Report of the External Commission of the Chamber of Deputies Destined to Investigate the Acquisition of Wood, Lumber Mills and Extensive Portions of Land in the Amazon by Asian Loggers. Brasilia, Brazil.
  4. Ritchie (2021) – Cutting down forests: what are the drivers of deforestation?
  5. Lindsay, R. (2004): From Forest to Field: How Fire is transforming the Amazon
  6. E. Sawe (2017): Countries sharing the Amazon
  7. Wikipedia (downloaded February 2024): Deforestation of the Amazon Rrainforest
  8. Borunda for National Geographic (2019, August 29): See how much of the Amazon is burning, how it compares to other years
  9. Feng, X., Merow, C., Liu, Z. et al. (2021). How deregulation, drought and increasing fire impact Amazonian biodiversity.
  10. Cai, W., Santoso, A., Collins, M. et al. (2021):  Changing El Niño–Southern Oscillation in a warming climate.
  11. Imperial College London (downloaded February, 2024): What is El Niño and how it is influenced by climate change? 
  12. Covey K, Soper F, Pangala S, et al. (2021): Carbon and Beyond: The Biogeochemistry of Climate in a Rapidly Changing Amazon. Front.
  13. The Guardian (2021, July 14): Amazon rainforest now emitting more CO2 than it absorbs.
  14. Gatti, L.V., Basso, L.S., Miller, J.B. et al. (2021): Amazonia as a carbon source linked to deforestation and climate change.
  15. M. Lapola et al. (2023): The drivers and impacts of Amazon forest degradation
  16. Rodriguez (2023, November 14): The Amazon’s record-setting drought: how bad will it be?
  17. Witze (2023, October 18): Greenland’s massive ice sheet is melting — here’s how to save it.
  18. United Nations News (2022, January 7): Climate change: For 25th year in a row, Greenland ice sheet shrinks
  19. Schmittner (2013): Modeling Effects Of Greenland Ice Sheet Melting On AMOC Variability And Predictability
  20. Moreno-Chamarro, E., J. Marshall, and T. L. Delworth, 2019: Linking ITCZ Migrations to the AMOC and North Atlantic/Pacific SST Decadal Variability. J. 
  21. Ciemer, C., Winkelmann, R., Kurths, J. et al. (2021): Impact of an AMOC weakening on the stability of the southern Amazon rainforest. 
  22. Adam for The Guardian (2009, March 11): Amazon could shrink by 85% due to climate change, scientists say
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