PART ONE

The key role of the Amazon rainforest for our planet.

By Günter Försterra & Vreni Häussermann

In recent months, the Amazon drought has caught headlines. But what does it mean for a typically wet area to experience a dry period? In this three-part blog series, our aim is to provide a comprehensive understanding of the situation: delving into the consequences of a diminishing Amazon rainforest, the various threats it faces, and the underlying causes. Furthermore, we’ll present potential solutions, some of which are within the grasp of every individual.

Understanding the Amazon: Significance and Threats

In the first part, let’s explore the significance of the Amazon, not only for South America but for the entire global community. We’ll examine the current threats looming over the Amazon rainforest and the potential consequences if it were to disappear.

Biodiversity Hotspot: The Amazon’s Richness

Spanning an area nearly as vast as the United States, the Amazon rainforest stands as the largest tropical rainforest on Earth, harboring over half of the world’s remaining rainforests (1). While the exact number of species inhabiting our planet remains unknown (as searching for life on Mars seems more enticing), we do know that species distribution isn’t uniform. Certain regions emerge as biodiversity hotspots, and the Amazon is a prime example, boasting an estimated 9% of all vertebrate species worldwide, 14% of all bird species, 13% of all fish species, 8% of all amphibians, and a staggering 22% of all vascular plant species (2).

Habitat Fragility: Vulnerability to Environmental Shifts

The coexistence of such a high number of species within a single ecosystem is made possible by most species specializing in narrow ecological niches or existing in small pockets within the region. Even minor shifts in environmental conditions can lead to the disappearance of certain niches or the transformation into habitats for other species, resulting in the displacement of the originally specialized species. If these shifts occur on a larger scale, with certain niches disappearing or altering across a broader region, specialized species face the threat of extinction within a relatively short period. Hence, even short-term weather extremes in an area with an otherwise stable climate can impose significant stress on certain species.

Diminished Habitat: Impact of Deforestation

This stress is exacerbated when the remaining habitat diminishes. Presently, somewhere between 17-20% of the original forest cover has already been lost (3). Despite deforestation rates witnessing a decline under President Lula in Brazil, roughly 10,000 km² of additional forest surface disappears each year, following a peak of 20,000 km² in 2019 due to intense forest fires (4). Another 14-17% of the forest is already disturbed or degraded to varying degrees (2), with disturbance causing as much biodiversity loss as deforestation itself (5,6).

Cloud Machine: The Amazon’s Role in Regional Climate

While a loss of 20% might not appear significant when considering that 80% of the forest still remains, the destruction is most severe at the forest edges, which harbor other niches compared to the central portions of the Amazon. Furthermore, the Amazon rainforest plays a pivotal role in its own climate. Between one-third and half of the rainfall in the Amazon originates within the basin itself, primarily through evapotranspiration from its vast leaf surface (7,8). Studies indicate that the forest’s resilience to recover from disturbances and climatic extremes has significantly diminished, with certain areas possibly beyond recovery (9,10,11).

If the Amazon were to lose between 20-25% of its original forest cover, its capacity to generate adequate rainfall for its own sustenance could be compromised. This would set off a gradual, irreversible process transforming at least the central and southern regions of the Amazon rainforest into a savanna-like ecosystem (12,13,14,15), capable of supporting only a fraction of the existing species.

Ecologic, Economic and Social Ramifications of Deforestation

Such a transformation would result in the extinction of millions of species, many of which remain undiscovered. The loss of the Amazon rainforest would not only entail the irrevocable destruction of biodiversity and the displacement of indigenous people who rely on the forest for their livelihood, but it would also have catastrophic regional and global climate impacts. Tropical rainforest soils tend to have limited water retention capabilities. Regional precipitation would dramatically decrease, leading to accelerated desertification.  In the absence of rain clouds, temperatures in Brazil could surge by an estimated two degrees on average, even without global warming, significantly affecting water supplies for major cities (16,17,18).

Amazon forest degradation can slash dry-season evapotranspiration by up to 34% and cause as much biodiversity loss as deforestation in human-modified landscapes, generating uneven socioeconomic burdens, mainly to forest dwellers (6).

In 2023, the World Bank published a report projecting economic losses due to deforestation in Brazil to soar to around 317 billion dollars per year, roughly seven times higher compared to the value of all commodities produced through deforestation. The report advocated for a non-deforestation-based economic strategy in the Amazon rainforest region (19,20).

 Climate Cascades: Potential Global Effects

As surface temperatures escalate, higher altitudes could experience drops in temperature, potentially triggering atmospheric wave effects. Predicting the precise outcomes of these effects proves challenging, but their implications could be profound. One model suggests that the loss of the Amazon rainforest, among other factors, could halve snow coverage in the Sierra Nevada, a critical water source for California (21).

Carbon Reservoir: The Role of the Amazon in Carbon Storage

Though mature tropical rainforests may not capture substantial amounts of carbon, their standing woody biomass represents an immense reservoir of fixed carbon. Various studies estimate that the Amazon stores between 120 and 150 gigatons of carbon, equivalent to 440-550 gigatons of CO2, which matches the total anthropogenic CO2 emissions over a span of 9-11 years (22)! However, when forests are burned or decomposed, they release this carbon in the form of CO2. Drying swamps emit additional CO2 and methane, a highly potent greenhouse gas.

With the current deforestation rate, the Amazon region has already shifted from being a carbon sink to a carbon source, emitting approximately 20% more greenhouse gases than it absorbs (23,24,25). Today, tropical deforestation accounts for about 13-20% of the annual global greenhouse gas emissions (26).

Clearly, there exist numerous compelling reasons to preserve the Amazon rainforest.

References

1. Mongabay (2021, June 22): The World’s Top 10 Biggest Rainforests
2. World Wildlife Fund (downloaded December 2023): What animals live in the Amazon?
3. World Wildlife Fund (downloaded December 2023): The Amazon in crisis: Forest loss threatens the region and the planet
4. Mongabay (2020, January 15): For final months of 2019, Amazon deforestation hits highest level in at least 13 years
5. Quintanilla, M., A. Guzmán León, C. Josse (2022): The Amazon against the clock: a Regional Assessment on Where and How to protect 80% by 2025
6. David M. Lapola et al. (2023): The drivers and impacts of Amazon forest degradation
7. Staal, A., Tuinenburg, O.A., Bosmans, J.H.C. et al. (2018): Forest-rainfall cascades buffer against drought across the Amazon. Nature Clim
8. Khand, K.; Numata, I.; Kjaersgaard, J.; Vourlitis, G.L. (2017): Dry Season Evapotranspiration Dynamics over Human-Impacted Landscapes in the Southern Amazon Using the Landsat-Based METRIC Model
9. Brando PM, Balch JK, Nepstad DC, et al. (2014): Abrupt increases in Amazonian tree mortality due to drought-fire interactions
10. Boulton, C.A., Lenton, T.M. & Boers, N. (2022): Pronounced loss of Amazon rainforest resilience since the early 2000s
11. Drüke, M., Sakschewski, B., von Bloh, W. et al. (2023): Fire may prevent future Amazon forest recovery after large-scale deforestation
12. Zhang K, de Almeida Castanho AD, Galbraith DR, et al. (2015): The fate of Amazonian ecosystems over the coming century arising from changes in climate, atmospheric CO2, and land use
13. Thomas E. Lovejoy, Carlos Nobre (2018): Amazon Tipping Point
14. Boers, N., Marwan, N., Barbosa, H. et al. (2017): A deforestation-induced tipping point for the South American monsoon system
15. The Guardian (2022, March 7): Climate crisis: Amazon rainforest tipping point is looming, data shows
16. Nobre, P., M. Malagutti, D. F. Urbano, et al. 2009: Amazon Deforestation and Climate Change in a Coupled Model Simulation
17. P. Artaxo (2023): Amazon deforestation implications in local/regional climate change
18. Alves de Oliveira, B.F., Bottino, M.J., Nobre, P. et al. (2021): Deforestation and climate change are projected to increase heat stress risk in the Brazilian Amazon.
19. Mongabay (2023, May 19): World Bank: Brazil faces $317 billion in annual losses to Amazon deforestation
20. Harusch, M. (2023): A Balancing Act for Brazil’s Amazonian States: An Economic Memorandum
21. Medvigy, D., R. L. Walko, M. J. Otte, & R. Avissar (2013): Simulated Changes in Northwest U.S. Climate in Response to Amazon Deforestation*
22. Emma Bryce for Scientific American (2023, February 20): Why Is the Amazon So Important for Climate Change? 
23. Covey K, Soper F, Pangala S, et al. (2021): Carbon and Beyond: The Biogeochemistry of Climate in a Rapidly Changing Amazon
24. The Guardian (2021, July 14): Amazon rainforest now emitting more CO2 than it absorbs
25. Gatti, L.V., Basso, L.S., Miller, J.B. et al. (2021): Amazonia as a carbon source linked to deforestation and climate change.
26. Measuring Carbon Emissions from Tropical Deforestation: An Overview

 

 

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The Amazon: what actually kills the rainforest?

The Amazon: what actually kills the rainforest?

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