Report on Amazon Rainforest Dieback and Implications for Sustainable Development Goals

1.0 Executive Summary

This report analyzes projections of Amazon rainforest dieback based on state-of-the-art Earth System Models (ESMs) under high-emission scenarios. The findings indicate a significant risk of large-scale ecosystem collapse, with severe implications for the achievement of the Sustainable Development Goals (SDGs), particularly SDG 13 (Climate Action) and SDG 15 (Life on Land). Nine of the twelve models analyzed project substantial rainforest dieback, characterized by a productivity decline of over 80%. The onset of this collapse is projected to occur within the 21st century, triggered by a combination of rising local temperatures, declining precipitation, and land-use changes. These results underscore the urgent need for global policy action to mitigate climate change and halt deforestation to prevent the crossing of critical ecological tipping points and safeguard global climate stability.

2.0 Analysis of Amazon Dieback Projections

2.1 Model Projections and Timelines

An analysis of twelve ESMs from the Coupled Model Intercomparison Project phases 5 and 6 (CMIP5 and CMIP6) reveals a strong consensus on the vulnerability of the Amazon rainforest. The key findings on the timing and extent of projected dieback are as follows:

• Prevalence of Dieback: Nine out of the twelve models project significant Amazon dieback by the end of the 23rd century.
• Spatial Extent: The projected dieback areas vary, with some models (HadGEM2-ES, CanESM5) predicting losses of up to two million square kilometers.
• Timing of Onset: The majority of models (six out of nine) project the onset of dieback to occur within the 21st century, with an average onset year of 2087 ± 49.
• Global Warming Threshold: The onset of dieback is associated with global warming levels ranging from 1.5°C to 10.2°C relative to pre-industrial levels, highlighting that critical thresholds could be crossed even under moderate warming scenarios, directly challenging the goals of SDG 13.

2.2 Climatic and Ecosystem Thresholds

The dieback is triggered when local climatic conditions exceed the physiological tolerance of the rainforest ecosystem. The study identifies specific thresholds that, if crossed, lead to a sustained decline in ecosystem productivity.

1. Temperature Threshold: Dieback is initiated when local annual surface air temperatures rise above a mean of 32.2 ± 4.8°C. Exceeding this thermal limit impairs photosynthesis and increases plant respiration, undermining the forest’s viability.
2. Precipitation Threshold: A decline in annual precipitation below a mean of 1394.3 ± 306.0 mm year⁻¹ is identified as a critical trigger. Reduced water availability induces drought stress, limits nutrient transport, and increases tree mortality.
3. Ecosystem Productivity Collapse: Dieback is defined as a greater than 80% decrease in Gross Primary Production (GPP), representing a near-total collapse of the forest’s ability to fix carbon and sustain itself. This directly impacts the ecosystem services vital for achieving SDG 15.

3.0 Primary Drivers and Mechanisms of Dieback

3.1 Climate-Related Drivers

The primary driver of the projected dieback is anthropogenic climate change, which alters large-scale atmospheric patterns and creates hostile conditions for the rainforest. This represents a failure to meet the objectives of SDG 13 (Climate Action).

• Regional Warming and Drying: All models project significant warming and drying in the Amazon basin, driven by global greenhouse gas emissions.
• Atmospheric Circulation Changes: A projected weakening of the Atlantic Meridional Overturning Circulation (AMOC) and a southward shift of the Intertropical Convergence Zone (ITCZ) are shown to reduce rainfall in the northern Amazon.
• Increased Climate Extremes: The intensification of El Niño-like conditions leads to more frequent and severe droughts and heatwaves across the entire basin, accelerating ecosystem stress.

3.2 Land-Use Change and Deforestation

Direct human pressures, particularly deforestation and land conversion for agriculture, significantly exacerbate the vulnerability of the Amazon. These activities are in direct conflict with SDG 15 (Life on Land), which calls for the sustainable management of forests and halting deforestation.

• Exacerbating Stress: Land-use change, as prescribed in the high-emission scenarios, contributes to dieback by reducing the forest’s resilience to climate stressors.
• Direct Forest Conversion: In some models, dieback occurs in grid cells directly converted to pasture or cropland, demonstrating that deforestation is a primary local driver of ecosystem loss.
• Undisturbed Forest Vulnerability: Significantly, several models project dieback even in areas with minimal direct land-use change, indicating that climate change alone is a sufficient driver to cause ecosystem collapse in undisturbed primary forests.

4.0 Implications for Sustainable Development Goals (SDGs)

4.1 SDG 13: Climate Action

The projected dieback of the Amazon rainforest represents a critical climate tipping point with severe consequences for global climate stability. The forest’s collapse would fundamentally undermine efforts to achieve SDG 13.

• Reversal of Carbon Sink: The Amazon is projected to shift from a vital carbon sink to a significant carbon source, releasing up to 0.5 GtC year⁻¹. This would create a positive feedback loop, accelerating global warming and making climate mitigation targets more difficult to achieve.
• Urgency of Emission Reductions: The findings highlight that high-emission pathways lead to irreversible ecosystem loss, demonstrating the absolute necessity of rapid and deep cuts in greenhouse gas emissions to keep global warming within safe limits.

4.2 SDG 15: Life on Land

The collapse of the Amazon ecosystem is a direct and catastrophic failure to meet the targets of SDG 15, which aims to protect, restore, and promote the sustainable use of terrestrial ecosystems.

• Biodiversity Loss: The dieback would result in an unprecedented loss of biodiversity (Target 15.5), as the Amazon is home to a significant portion of the world’s terrestrial species.
• Deforestation and Degradation: The process represents the ultimate form of forest degradation and loss, directly contravening the goal of halting deforestation and restoring degraded forests (Target 15.2).
• Loss of Ecosystem Services: The collapse would eliminate critical ecosystem services, including climate regulation, water cycling, and the provision of resources for local and indigenous communities.

4.3 Interconnected SDG Impacts

The consequences of Amazon dieback extend beyond climate and land, affecting a range of interconnected SDGs.

• SDG 2 (Zero Hunger): Altered precipitation patterns could disrupt regional agriculture, impacting food security.
• SDG 12 (Responsible Consumption and Production): The role of land conversion for agriculture highlights the link between unsustainable consumption patterns and ecosystem destruction.
• SDG 17 (Partnerships for the Goals): This research, utilizing global collaborative modeling projects like CMIP, exemplifies the international scientific cooperation needed to address complex global challenges.

5.0 Conclusion and Policy Recommendations

The evidence from Earth System Models presents a stark warning: continued high greenhouse gas emissions and deforestation place the Amazon rainforest at high risk of a large-scale, potentially irreversible dieback. Such an event would have devastating consequences for global biodiversity, climate stability, and the achievement of the Sustainable Development Goals.

Urgent and integrated policy action is required to:

1. Accelerate Climate Mitigation: Vigorously pursue emission reduction pathways consistent with limiting global warming to 1.5°C, in line with SDG 13, to keep the Amazon’s climate within its resilience thresholds.
2. Halt Deforestation: Implement and enforce strong policies to end deforestation and forest degradation, promoting sustainable land management practices as mandated by SDG 15.
3. Enhance Model Development: Improve the representation of key processes like fire dynamics, nutrient limitations, and drought-induced mortality in ESMs to refine projections and better inform risk assessments.

Protecting the Amazon rainforest is indispensable for a sustainable future and requires immediate and concerted global effort.

Analysis of Sustainable Development Goals in the Article

1. Which SDGs are addressed or connected to the issues highlighted in the article?

The article primarily addresses issues related to two Sustainable Development Goals (SDGs):

• SDG 13: Climate Action
  
  The article’s central theme is the impact of climate change on the Amazon rainforest. It explicitly discusses “high-emission scenarios,” “global warming levels,” rising “surface air temperatures,” and the role of the Amazon in “climate regulation” and the “global climate and carbon cycle.” The study’s projections of Amazon dieback are a direct consequence of climate change, making SDG 13 a core focus. The article states, “The Amazon rainforest, the world’s largest tropical forest, plays a crucial role in climate regulation but faces risks of dieback under climate change.” This directly links the ecosystem’s health to global climate stability.
• SDG 15: Life on Land
  
  This goal is concerned with protecting, restoring, and promoting the sustainable use of terrestrial ecosystems, sustainably managing forests, combating desertification, and halting biodiversity loss. The article is entirely focused on the “Amazon rainforest, the world’s largest tropical forest,” examining threats like “deforestation,” “fires,” “loss of biodiversity,” and “ecosystem collapse.” The concept of “dieback” itself signifies a massive degradation of a terrestrial ecosystem. The text highlights that disturbances like “droughts, fires and deforestation” are “aggravating stress on the forest, potentially pushing it closer to a tipping point.”

2. What specific targets under those SDGs can be identified based on the article’s content?

Based on the article’s discussion, several specific targets under SDG 13 and SDG 15 are relevant:

1. Under SDG 13: Climate Action
   • Target 13.1: Strengthen resilience and adaptive capacity to climate-related hazards and natural disasters in all countries.
     
     The article directly addresses this by analyzing the Amazon’s declining resilience. It states that “temperature rise, precipitation decline and land-use disturbances” are “key drivers reducing Amazon resilience.” The study investigates the “tipping point” beyond which the ecosystem cannot recover, which is a core concept of resilience.
   • Target 13.2: Integrate climate change measures into national policies, strategies and planning.
     
     While not discussing policies directly, the article’s conclusion provides a clear scientific basis for such integration. It states, “urgent policy action is needed to limit warming and deforestation, reducing the risk of tipping points and large-scale collapse.” This highlights the necessity of using scientific findings, like those presented, to inform policy.
2. Under SDG 15: Life on Land
   • Target 15.1: By 2020, ensure the conservation, restoration and sustainable use of terrestrial and inland freshwater ecosystems and their services, in particular forests, wetlands, mountains and drylands, in line with obligations under international agreements.
     
     The entire study is an examination of the threats to the conservation of the Amazon forest ecosystem. The projection of dieback, covering “up to two million km²,” represents a catastrophic failure to conserve this vital terrestrial ecosystem.
   • Target 15.2: By 2020, promote the implementation of sustainable management of all types of forests, halt deforestation, restore degraded forests and substantially increase afforestation and reforestation globally.
     
     The article explicitly identifies “deforestation” and “land-use change (LUC)” as key drivers exacerbating dieback. It notes that in some models, dieback is “primarily driven by the LUC, i.e. conversion of primary vegetation to pastures and crops.” This directly connects the failure to halt deforestation with the risk of ecosystem collapse.
   • Target 15.3: By 2030, combat desertification, restore degraded land and soil, including land affected by desertification, drought and floods, and strive to achieve a land degradation-neutral world.
     
     The article discusses mechanisms that align with desertification and land degradation, such as “prolonged and intensified dry seasons” and “regional drying.” It uses the Köppen-Geiger climate classification to show a “clear shift from tropical to arid climate categories” in regions experiencing dieback, effectively describing a process of climate-driven desertification.
   • Target 15.5: Take urgent and significant action to reduce the degradation of natural habitats, halt the loss of biodiversity and, by 2020, protect and prevent the extinction of threatened species.
     
     The projected “Amazon dieback” is a prime example of large-scale degradation of a natural habitat. The article mentions that climate change poses risks such as “loss of biodiversity and ecosystem collapse,” directly linking the forest’s decline to this target.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

Yes, the article is rich with quantitative data and metrics that can serve as indicators for measuring progress toward the identified targets.

• Global Warming Level (°C): The article identifies the onset of dieback occurring at “global warming levels ranging from 1.5 to 10.2 °C.” This serves as a direct indicator for Target 13.1, linking a global climate metric to ecosystem resilience.
• Local Climatic Thresholds (Temperature and Precipitation): The study identifies specific local thresholds for dieback onset: “local surface air temperatures above 32.2 ± 4.8 °C and precipitation below 1394.3 ± 306.0 mm year−1.” These are measurable indicators of climate-related hazards affecting the ecosystem (Target 13.1 and 15.3).
• Gross Primary Production (GPP): The study’s primary metric for dieback is an “over 80% decrease in gross primary production (GPP).” GPP (measured in kgC m⁻² year⁻¹) is a direct indicator of ecosystem health, productivity, and degradation, relevant to Targets 15.1 and 15.5.
• Land Cover/Use Change: The article analyzes the impact of LUC, mentioning “conversion of primary vegetation to pastures and crops” and changes in “crop area fraction.” The percentage of forest cover loss or conversion is a key indicator for Target 15.2 (halting deforestation).
• Net Carbon Flux: The projection that the Amazon dieback region could shift “from a carbon sink to a temporary carbon source of up to 0.5 GtC year⁻¹” is a critical indicator. It measures the forest’s function in the global carbon cycle, relevant to both SDG 13 (as a climate feedback) and SDG 15 (as an ecosystem service).
• Area of Forest Dieback (km²): The article quantifies the potential spatial extent of dieback, with some models projecting areas “covering up to two million km².” The total area of degraded or lost forest is a fundamental indicator for Targets 15.1, 15.2, and 15.5.
• Köppen-Geiger Climate Classification: The analysis of shifts in climate zones (e.g., from tropical rainforest to tropical savanna or arid) serves as an indicator of fundamental, long-term changes in environmental conditions that undermine ecosystem stability, relevant to Target 15.3.

4. Summary Table of SDGs, Targets, and Indicators

Source: nature.com