Novelty in ecosystems, and its implications for biodiversity conservation
Ecologists are usually pretty easy-going, maybe even staid. Which makes it all the more surprising that two vicious debates erupted in recent years, both resulting in bitter divisions. Among restoration ecologists the idea of ‘novel ecosystems’ has been the point of contention. For its proponents, novel ecosystems represent “the new ecological world order” and even a useful “propaganda tool”. For its opponents, novel ecosystems are “a Trojan horse for conservation”, and they claim that “the road to confusion is paved with novel ecosystems label”. Among conservation biologists, a different debate has been brewing around the notion of ‘new conservation’ that has resulted in similarly charged rhetoric. Proponents of new conservation claim that “conservation is failing”, while its opponents argue against “the hubris of the managerial mindset” embedded in new conservation. How did we get here and what is really going on?
At the heart of both debates is the question what to do with places that have been changed greatly by people. A restoration ecologist’s mission is to undo these changes and bring ecosystems back to a historic baseline. This is rarely easy, not always successful, and often feels like Sisyphean task. Maybe this sense of futility is what led some restoration ecologists, Richard Hobbs being the most vocal among them, to assert that there are some ecosystems that have changed so much that they can no longer be restored. To Hobbs these are novel ecosystems, they represent the new ecological world order, and they should be managed for their ecological benefits to people, rather than trying to restore them. Hobbs advocates that we should embrace novel ecosystems, and other proponents go as far as to encourage using this term as a propaganda tool to change attitudes towards heavily altered ecosystems, full of non-native species and that may be radically altered relative to “pristine” ecosystems. Not surprisingly, those inspired by the goal to restore what has been lost have found Hobbs’ notion of novel ecosystems wanting if not downright dangerous. What has ensued is an exchange in the academic literature that has been lively, to say the least. However, rather than to debate the fair question what ecosystems should be managed for, and if they have a value in their own right, or if only the benefits that they provide to people matter, the question of how to define a novel ecosystem has become the center of this debate. What a missed opportunity!
At the same time as these discussions about novel ecosystems were occurring among restoration ecologists, conservation biologists fought about the idea of ‘new conservation’. The parallels in these two debates are striking. A key mission of conservation biologists, motivated by the loss of so many wild places, has been to protect places that have remained relatively unchanged. However, Peter Kareiva and colleagues asserted that this conception of conservation was just as futile as the goal of restore ecosystems in a world where pollution is everywhere, and climate change is looming. Mixed into the fray is the concept of the “Anthropocene”. That is, the notion that people are now shaping this planet so much that this is becoming evident in the geological record; we are thus entering a new geological epoch. The proposed alternative to ‘old conservation’ with its focus on protected areas? You guessed it: to manage places for their ecosystem benefits, and to make conservation more “people friendly”. And the reaction of other conservation biologists? About as much enthusiasm as restoration ecologists had toward Hobbs’ idea of novel ecosystem. “With rhetorical fists swinging” an entire book now argues against new conservation. Yikes! Another missed opportunity indeed, and a discussion full of rhetorical straw men, and historical falsehoods.
As fun as bar fights like these can be, maybe it is time to step back from both debates. Creating false dichotomies between novel ecosystems and those that are not, or new conservation versus old, leads neither restoration nor conservation forward.
One point that has been lost in these debates is the key distinction between change and novelty. Furthermore, when talking about novelty what has been missing is specificity: novel in what aspects and relative to what? And most importantly perhaps, it is time to discuss is the degrees of novelty rather than simplify the world around us into crude black-and-white dichotomies and what is novel versus what is not..
Novelty is the degree of dissimilarity of a system, measured in one or more dimensions, relative to a reference baseline defined both in time and space.
Novelty is different from change. Yes, humans have changed every place on the planet in some ways, but some places have clearly changed a lot more than others. But not all changes result in novelty. A perfect example is global warming. Nowhere have temperatures risen more than in the Arctic. However, temperatures in the Arctic are also extremely variable within a given day, a year, and millennia. Relative to this variability, the absolute temperature increases have not been very high, and there are other places that are currently as warm as the Arctic is on track to becoming. The Tropics offer a contrast. At lower latitudes absolute temperature increases have been fairly minor, but variability in temperatures is also low at various temporal and spatial scales. This makes the relative changes larger and there is nowhere a precedent for warmer tropics. What this means is that while changes in temperatures are highest in the Arctic, novelty in temperature is highest in the tropics.
Novel in which way? Ultimately, this depends on the specific question at hand, but the distinction of abiotic versus biotic novelty is an important one. While climate change is a perfect example of abiotic novelty, so is rising atmospheric nitrogen deposition, ocean acidification, changes in river flow regimes, and fire suppression. Non-native species are a perfect example of biotic novelty, and so are extirpations of top carnivores, or urban bird communities with species compositions that are fundamentally different from those found in nearby forests. Abiotic novelty may ultimately lead to biotic novelty, but biotic novelty does not always depend on it. For conservationists, abiotic novelty can pose vexing problems because its effects may be both outside of their control, and difficult to predict because there is no good reference. The key point is though that it is not meaningful to talk about novelty in an ecosystem without being specific in which way it is novel.
Novel relative to what? Similar to the need to be specific in which way an ecosystem is novel, talking about novelty is only meaningful when defining a reference baseline in both time and space for comparison. With respect to time, one reference baseline that is commonly invoked, especially in North America, is the period prior to European settlement. This is a favorite reference point because changes thereafter were so rapid and drastic, but also because the myth of a pristine wilderness before 1492 is comforting. For species, however, a deeper baseline may be more relevant in order to measure the degree of novelty relative to conditions experienced over the evolutionary history of that species. In contrast, for a land manager, the time that he or she lived in a given place is often the baseline that is used to compare change against. In space, an obvious comparison is evaluating the current conditions against what was in the same place at some time before, and when changes exceed the historical range of variability of that place, then it is locally novel. However, taking a broader spatial look is also informative, since conditions may be novel for a given region, continent, or even globally.
We propose that by separating novelty clearly from change, and being specific when talking about novelty, we can have more productive discussions relevant to conservation and restoration alike. Novelty is real. We cannot just wish it away and ignore it. But it is not helpful either to throw our hands up and indiscriminately embrace the places that are highly novel in order to escape the world of wounds that those with an ecological education live in. Fierce realism, and rigor in our thoughts and actions are the only way forward, and offer a way out of the trench warfare that the debates about novel ecosystems and new conservation have ended up in.
This goal of this webpage is to offer a new, more quantitative view on novelty in ecosystems. We explore here what causes novelty in ecosystems, how we can measure it, and what it means for natural resource management and biodiversity conservation. The ideas put forward here arose in lively discussions among the participants in the NSF IGERT funded graduate training program on novel ecosystems at the University of Wisconsin-Madison.