“Innovating” Biodiversity: A brief dive into rewilding (part I)
This four-part post is the result of ongoing conversations I’ve been having with friends and colleagues since I was at COP26 this past November. When I was a master’s student at Oxford, rewilding was all the rage among a niche set of environmentalists (sort of like mycology enthusiasts today), with our programme director being especially keen — hence, my reasonable familiarity with it.
While I’m surprised to hear rewilding is trending again outside of its usual environmental science and conservation circles, I’m also excited that more mainstream folks are asking questions about this concept. It seems like it has good potential to be part of a wider, transferable toolkit for climate change adaptation and mitigation strategies worldwide. Part two is available here, Part 3 here, and Part 4 here (TBC). Read on — and as always, let me know your follow-up questions!
Scene 1: Setting the Stage (i.e., the background science)
What are planetary boundaries?
In 2009, Dr. Johan Rockström¹ and colleagues proposed a new framework for understanding how to manage humans’ activities on Earth if we wanted to continue living within the Earth’s sustainable biological thresholds.
Their paper, published in the leading multidisciplinary science journal Nature, described and quantified nine complex, interconnected Earth systems systems that must be in balance to ensure human survival. Exceeding these systems’ thresholds, they warned, would upset this complex system and leave Earth an inhabitable place for humans. Among the ten biological thresholds these scientists identified included ocean acidification, global freshwater use, biodiversity loss, and — of course — climate change.
Since publishing their paper, pressures on these nine systems have continued to escalate. As the most recent 6th IPCC report (2021) highlights, specific human activities have changed the Earth’s climate in multiple unprecedented (and in some cases, irreversible) ways, leading to a increase in extreme weather and climate-related events that is predicted to further intensify. Sea levels have risen at a rate nearly triple that compared to 1901–1971. Global surface temperatures between 2011–2020 were 1.09⁰C hotter than between the years 1850–1900. The list goes on.
By the mid-2010s, sufficient new data on these environmental changes had been collected that Dr. Will Steffen and colleagues (including Dr. Rockstrom — academia is a small world) published a follow-up paper to Rockstrom et al.’s original paper in Science in 2015. With an eye towards helping guide global policymakers in sustainable development, this new study updated and extended analyses of the original proposed planetary boundaries based on the new environmental data available by the mid-2010s (as presented in Figure 1 below).
What these scientists found were that four of the existing planetary boundaries had exceeded the proposed limits from which existing Earth systems could reasonably recover. (These are highlighted in red and yellow in Figure 1.²) The four systems included 1) biogeochemical flows and 2) land-system change, as well as two “core” planetary boundaries that are integral to the overall functioning of Earth systems: 3) climate change and 4) biodiversity integrity.
In summarizing what “exceeding these limits” meant for global policy makers (as well as humanity more generally), Steffen et al. were careful to explain that their paper’s focus was on pointing out evidence and highlighting the substantial risks to society posed by exceeding such planetary boundaries. As they stated in their paper:
“Planetary boundaries are scientifically based levels of human perturbation of the Earth system beyond which Earth system functioning may be substantially altered. Transgression of the planetary boundaries thus creates substantial risk of destabilizing the Holocene state [our current geological epoch, lasting since the last major glacial period] of the Earth systems in which modern societies have evolved.
The planetary boundaries framework does not dictate how societies should develop. These are political decisions that must include consideration of the human dimensions, including equity, not incorporated in the planetary boundaries framework. Nevertheless, by identifying a safe operating space for humanity on Earth, the planetary boundaries framework can make a valuable contribution to decision-makers in charting desirable courses for societal development.”
— emphasis added; excerpt from Steffen et al. (2015) [DOI: 10.1126/science.1259855]
While not explicitly directing global decision-makers on which actions to take, these scientists were exceedingly clear in identifying (i) where significant and credible threats exist that are violating these planetary boundaries, and (ii) which of these boundaries need to be immediately addressed to help society continue to develop in a self-sustaining manner.
How do we re-balancing Earth systems?
Even if you’ve come across these studies before, at this point you may asking yourself (like my undergrad students sometimes do during class), “Where do we go from here? This outlook seems rather… bleak.” You wouldn’t be wrong. Existing global environmental data analyses (such as those summarized in the IPCC’s various reports) make a compelling case for immediate actions to prevent further catastrophic and irreversible changes to the four Earth systems whose boundaries have already been exceeded. Yet, before we go any further, let’s first clarify what actually is being talked about when we mention these essential Earth systems.
Underpinning Rockström et al.’s planetary boundaries framework are a series of complex, interdependent environmental systems that keep life on this planet self-sustaining. Our current scientific classifications roughly group these Earth systems into taking place across five main spheres.³ These include:
- The atmosphere (i.e., the layers of gases surrounding the Earth),
- The cryosphere (i.e., the parts of Earth where water is in solid form),
- The biosphere (i.e., the parts of the Earth where life exists),
- The geosphere (i.e, the Earth itself), and
- The hydrosphere (i.e., all water on Earth).
While current scientific convention separates these systems into different disciplines and research areas for ease of being able to know who’s studying what, it’s worth remembering that they are, in fact, all interconnected. For example: The cryosphere (i.e., where water is in solid form) is also contained within the hydrosphere (i.e., all the water on Earth), but research on the crysophere specifically goes to a deeper level of complexity in understanding the frozen water parts of Earth.
Understandably, each of these complex Earth systems has its own nuances that environmental scientists are continuing to explore. By testing and validating what we know about each via the scientific method, we’re able to systematically build up a transferable body of knowledge that can help inform best practices in conservation efforts worldwide.² This knowledge helps us create an increasingly accurate and refined understanding of each of these different Earth systems, and is a crucial first step in how we as humans can go about bringing Earth’s planetary boundaries back within their sustainable limits... or, if necessary, assisting society globally in adapting to the consequences that disrupting these Earth systems has and will continue to bring. (More on that in part two.)
Additional Notes
[1] Though I haven’t yet had the chance to meet Johan Rockström (and don’t know him personally), I do enjoy following updates on his usually very timely research via his personal account on Twitter as well as via his work with the Stockholm Resilience Centre and as Director of the Potsdam Institute for Climate Impact Research. Good stuff.
[2] The ‘question mark’ areas of Figure 1 represent areas where insufficient or inconclusive data were available, and thus no strong conclusions could be claimed. Remember: correlation does not imply causation.
[3] For a slightly more nuanced take on what exactly we mean by Earth systems, I’d recommend checking out Steffen et al.’s 2020 academic paper on “The emergence and evolution of Earth System Science.” The authors cover the evolution of Earth System Science (ESS) as a discipline from the 1980s to the present in significantly more detail than I go into here. If this is your jam, this is a great paper to go geek out on.
