Planetary boundaries: where do we stand on biodiversity?
What are the 9 “planetary boundaries”?
Planetary boundaries are a scientific concept defining the environmental limits within which humanity can safely operate. The concept was introduced by a group of environmental scientists led by Johan Rockström from the Stockholm Resilience Centre in 2009.
Boundaries are interrelated processes within the complex biophysical Earth system: there are 9 planetary boundaries that are critical for maintaining the stability and resilience of the Earth's systems, as shown below.
Source: Stockholm Resilience Centre; based on Richardson et al. 2023 - Current status of control variables for all nine planetary boundaries
The evolution of those 9 ecological processes is measured by control variables (i.e. suitable proxys for measurement). Once a certain critical threshold is crossed, there is a risk that these processes may shift and reorganize abruptly and irreversibly. Their exact values are unknown. Instead, there is a reference to a “risk zone”, with a low limit beyond which we leave the "safe" zone and a high limit before entering the danger zone. Crossing these boundaries increases the risk of causing large-scale, potentially irreversible environmental changes. And all of the 9 planetary boundaries are presently significantly perturbed by human activities and for 6 of them boundary had been crossed.
Where do we stand on the “biodiversity” planetary boundary?
One of the 9 boundaries is about “biosphere integrity”. It refers to the ability of Earth's ecosystems to maintain their natural states, functions, and processes that support the diversity of life. It is considered one of the "core boundaries" because biodiversity underpins the resilience of ecosystems and their ability to provide essential services, such as carbon sequestration, water purification, and climate regulation.
It is split into 2 components:
Genetic integrity: it refers to the genetic diversity within and between species, which is vital for the adaptability and evolution of species in response to environmental changes. In the framework, it is measured as the maximum extinction rate compatible with preserving the genetic basis of the biosphere’s ecological complexity.
The “suggested” boundary level is <10 E/MSY (extinctions per million species-years).
Functional integrity: it refers to the variety of biological functions and processes carried out by different species within an ecosystem, which guarantees its stability (ecosystem condition). Historically it was thought to be measured using the Biodiversity Intactness Index (BII), which measures the average abundance of originally present species across a range of ecosystems. However, the BII has been fairly criticized as a control variable; scientists are now considering a new indicator with a computable proxy for photosynthetic energy and materials flow into the biosphere, i.e. Net Primary Production (NPP); they define the functional component of the biosphere integrity boundary as a limit to the human appropriation of the biosphere's NPP (HANPP) as a fraction of its Holocene NPP (more information on this can be found is this article) .
The boundary for functional integrity is not precisely quantified in the framework but is suggested to be maintained at a level where 90% of biodiversity is intact.
Additionally, it is worth mentioning that biodiversity is also indirectly included in others boundaries as many of them are direct drivers of biodiversity loss: land-system change, freshwater use, climate change, biogeochemical flows (phosphorus and nitrogen pollution) etc.
The boundary for Land-system change is measured as the % of remaining forest cover relative to potential natural forest cover in three major biomes: tropical, temperate, and boreal forests (set respectively at 85% / 50% / 85% of original forest cover).
Current estimates suggest we have crossed the “planetary boundary” for 6 out of 9 of the planetary boundaries including climate change, land-system change, and biodiversity integrity, on both of its variables:
The current rate of species extinctions is estimated to be at least 10 to 100 of times higher than the average rate over the past 10 million years and is accelerating, so the current value for the extinction rate sits at >100 E/MSY: the genetic component of the biosphere integrity boundary is significantly exceeded.
If there is still some work to be done to estimate the boundary based on the HANPP considering all three realms, there is consensus on the fact that the boundary is crossed as well for the functional integrity.
💡 What are tipping points? The issue is those impacts on biodiversity can be locally irreversible: ecosystems may reach "tipping points" beyond which recovery is impossible, such as when a deteriorating forest transforms into a desert. The complex and non-linear dynamics of these interactions within biodiversity and nature render these specific tipping points challenging to forecast. However, on a broader scale, scientists believe that it is still feasible to return within the planet's safe operating boundary, which is encouraging news: we can act upon biodiversity and see results fairly quickly.
Why is it the framework of planetary boundaries so powerful? How does it fit with other biodiversity reporting & disclosure frameworks?
At darwin, we strongly believe that the planetary boundaries framework is a powerful concept as:
It embraces an holistic approach: anthropogenic perturbations of the global environment are typically addressed as if they were separate issues, e.g., climate change, biodiversity loss, or pollution. This framework integrates various Earth system processes into a single model, recognizing that these processes are interconnected. This also means that a global focus on climate change alone is not sufficient for sustainability.
It’s robust scientifically: it’s based on rigorous scientific research and uses control variables to define thresholds for each boundary. As a result, the framework provides a scientific basis for environmental governance and policymaking.
As a result, leading regulatory frameworks are increasingly integrating the concept of planetary boundaries, encouraging businesses to explore the interconnected nature of risks and impacts in all areas of sustainability.
The CSRD makes an explicit reference to the alignement to planetary boundaries as a key objective of the biodiversity standard ESRS E4. It covers a range of topics that integrates some of the key planetary boundaries via its 5 environmental standards.
The TNFD explicitly integrates the planetary boundaries framework to highlight the nature-related risks that arise when these boundaries are crossed. For example, it addresses issues such as biodiversity loss, freshwater use, and biogeochemical flows, which are all part of the planetary boundaries.
Indirectly, while it does not explicitly name the planetary boundaries framework, ISSB IFRS 1 and IFRS 2 goes beyond carbon & climate change to encourage reporting of any ESG-related risk or opportunity.
How do we use this framework at darwin?
At darwin, we believe planetary boundaries should be integrated into business strategy. More specifically, our target setting module will help designing targets aligned with the Science Based Targets for Nature (SBTN) framework which specific purpose is to translate planetary boundaries into targets and trajectories applicable to corporates. You can check our article on this here.
