The Amazon: Why it matters to our climate - The Climate Question podcast, BBC World Service

Key Concepts

• Amazon Rainforest: The world's largest rainforest, vital for global climate regulation and biodiversity.
• Biodiversity: The variety of plant and animal life in a particular habitat.
• Carbon Sink: A natural reservoir that accumulates and stores carbon-containing chemical compounds for an indefinite period.
• Deforestation: The clearing of forests for other land uses.
• Tipping Point: A critical threshold beyond which a system undergoes irreversible change.
• El Niño: A climate pattern characterized by unusually warm ocean temperatures in the central and eastern tropical Pacific Ocean, which can lead to drier conditions in the Amazon.
• Leaf Litter: The layer of dead leaves, twigs, and other organic material on the forest floor.

The Amazon: A Vital Ecosystem Under Threat

This summary delves into the critical importance of the Amazon rainforest, its immense biodiversity, its role in climate regulation, and the escalating threats it faces, particularly from deforestation and fires, exacerbated by climate change. Dr. Erika Berenguer, a rainforest expert from Brazil, provides detailed insights into these issues.

Biodiversity and Its Importance

The Amazon is highlighted as the most biodiverse region on Earth, housing an unparalleled range of plant and animal species. This biodiversity is crucial for several reasons:

• Utilitarian Value: Many species have direct practical applications. For instance, snake venoms are used in antidepressants, impacting the pharmaceutical industry.
• Aesthetic Value: The natural beauty of the Amazon attracts tourism, contributing to local economies and providing aesthetic pleasure.
• Intrinsic Value: Each species has an inherent right to exist, regardless of its direct usefulness to humans.

The Amazon's extraordinary biodiversity is attributed to its vast size and long evolutionary history. Its geological past, transitioning from ocean to swamp to forest, coupled with its massive rivers acting as natural barriers, has led to the speciation of many similar species on opposite banks.

The Amazon's Role in Climate Regulation

The Amazon plays a pivotal role in regulating the global climate through several mechanisms:

• Carbon Storage: The rainforest stores an immense amount of carbon. Deforestation of the entire Amazon could release an amount of CO2 equivalent to 10 years of global emissions. Individual large trees can store 3 to 5 tonnes of carbon.
• Carbon Sequestration: Through photosynthesis, trees absorb CO2 from the atmosphere, acting as a massive carbon sink. Rainforests have been critical in slowing the impact of climate change by removing a third of CO2 emissions between 2010 and 2019.
• Rainfall Generation: Forests are significant climate regulators, particularly in generating rainfall. The water released through transpiration from leaves creates morning fog and contributes to higher rainfall levels within a 100 km radius of forests. This rainfall generation extends far beyond the Amazon basin, influencing regions as far north as Texas and contributing significantly to the La Plata Basin (Uruguay and Argentina).
• Energy Production: For Brazil, a major source of electricity comes from hydroelectric dams, which are dependent on consistent rainfall generated by the Amazon.

Threats to the Amazon: Deforestation and Fires

The Amazon is facing severe threats, primarily from human activities:

• Deforestation: Driven by agriculture, particularly soybean cultivation, and other land-use changes, deforestation is a major concern. The "arc of deforestation" in the southern Amazon is particularly affected.
• Fires: Paradoxically, one of the wettest places on Earth is experiencing increasing fires. This is linked to climate change making the Amazon drier.
  • Mechanism: Increased temperatures (up to 1.5°C average increase across the basin since the 1970s, with maximum temperatures rising by 3°C in some regions) draw more water out of vegetation and the leaf litter, turning it into dry fuel.
  • Human Ignition: All fires in the Amazon are human-ignited. While historically fires were used by traditional populations for subsistence farming and were contained by the wet leaf litter, climate change allows these fires to propagate uncontrollably into the forest.
  • Lack of Co-evolution: Unlike ecosystems that have evolved with fire (e.g., Californian forests), the Amazon's flora has not developed natural fire-resistance mechanisms due to its historically wet environment.

The Impact of Fires and Drying

The consequences of increased fires and drying are profound:

• Loss of Carbon Sink: The Amazon is at risk of becoming a net emitter of carbon rather than a sink, especially during El Niño years which exacerbate dryness.
• Devastating Anecdotes: Dr. Berenguer shares a poignant story of a massive tree, over 30 meters tall, that survived a fire in 2015 but was lost in another El Niño event in 2023, highlighting the scale of destruction.
• Global Emissions: Emissions from fires in a single region of the Amazon during the 2015 El Niño were equivalent to the 13th most polluting country globally, surpassing the UK.
• Health Impacts: Thick smoke from fires leads to severe respiratory issues, with a 200% increase in hospital admissions for children under five due to respiratory problems. This also impacts the workforce as parents take time off to care for sick children.
• Accidents: Smoke on highways has led to an increase in traffic accidents, including a fatal incident involving a driver en route to fight fires.

The Tipping Point

A critical concern is the potential for the Amazon to reach a "tipping point."

• Definition: This is the threshold where the Amazon can no longer generate enough rainfall to sustain itself as a rainforest, transitioning into a novel, drier ecosystem.
• Regional Variation: The tipping point is not uniform across the 7 million square kilometer Amazon. Some areas, particularly in the south within the "arc of deforestation," are showing signs of reaching this point due to high deforestation rates and increased temperatures.
• Irreversible Change: While the exact timing is uncertain, the scientific community believes parts of the Amazon are approaching this irreversible state. Dr. Berenguer emphasizes that knowing the exact distance to a cliff is less important than knowing it's there and needing to stop.

What Can Be Done?

The primary solution to save the Amazon rainforest is to reduce global emissions.

• Global Action: Without reducing global emissions, temperatures will continue to rise, leading to drier conditions and more prevalent fires, even if deforestation is reduced.
• Urgency: The message is clear: immediate action to reduce emissions is paramount to prevent the Amazon from falling off the cliff.

The discussion concludes with a call to action for global emission reduction as the most critical step in preserving the Amazon.