Can rewilding stop climate change?

What is rewilding?

Rewilding (re-wilding) is the theory and practice of conserving nature by excluding the most extensive areas of the Earth from human interference as possible. Proponents of this approach believe that nature itself will rebuild ecosystems ravaged by humans, remove invasive alien species, chemical, noise, light pollution. However, it will have to be helped in the first stage of the process – to compensate for the losses inflicted by previous generations. This assistance is not only to leave the areas in question alone, defending them from polluters and poachers, but also several other active protection measures. The most common are:

• Reintroductions of extinct species in a feral area;
• Introducing replacements for extinct species where restitution of the original taxon is impossible, e.g.: mammoth, saber-toothed tiger;
• Restoration of transverse and longitudinal patency of rivers through demolition of dams, introduction of new dams and modernization of existing culverts, pushing back embankments, restoration of meanders and oxbow lakes;
• Introducing artificial, but as close to nature as possible, shelters for selected groups of species, e.g.: boxes for birds and bats, nesting platforms for water birds, hotels for wild pollinators and spiders, spawning grounds for fish, ponds for amphibians;
• Removal of invasive alien species, or at least control of their further spread;
• Promotion of a nature-friendly economy.

Rewilding concepts will be implemented within the framework of the UN Decade for Ecosystem Restoration 2021 – 2030 and the new EU Biodiversity Strategy 2030, including the Community Wildlife Restoration Plan.

Pandora’s box?

Among scientists and activists, who have been involved for many years in conservation issues, saving species and entire ecosystems, there are voices cooling their enthusiasm for rewilding. According to critics – including Simberloff, a popularizer and one of the creators of the term “flagship genre” (English. flagship species) – organisms introduced into a given ecosystem after hundreds or thousands of years of absence, under slightly different climatic conditions, can bring more losses than benefits to biocenoses and biotopes, not to mention new threats to humans. Rewilding may also condemn nature to further pressure from alien species[1].

A Copernican coup in global rewilding?

In rewilding selected areas and in day-to-day wildlife work, the prevailing attitude is that it is our duty to save remnant populations of free-ranging animals from human pressures, including global and local climate change.

A completely different perspective on the problem is offered by an international team of scientists led by Schmitz, who published a paper in Nature Climate Change on the importance of restoring wildlife and their functional roles in carbon sequestration. Schmitz and co-authors[2] propose a reversal of the previous approach, positing that it is not so much the species that are to be protected from undesirable climate change, but the restoration of populations of selected groups of animals (the so-called keystone, keystone species) that is to halt and, over time, reverse these changes. Active conservation of keystone species (and consequently entire ecosystems dependent on them) is intended to be a technically easier and cheaper alternative to industrial capture and storage of greenhouse gases and the transition to a low-carbon closed-loop economy.

_CO2 sequestration: animals instead of industrial facilities

Schmitz and co-authors’ idea may be attractive to many practitioners and policymakers. Some of the most promising greenhouse gas capture and storage technologies are still at the prototype stage. Others sometimes require rare metals that are difficult for the EU and the US to access, i.e. 17 elements with similar chemical properties that are essential for modern industry and communications, including transportation electrification (contrary to their traditional name, they are not all rare in the Earth’s crust; instead, they are all difficult to extract in an economically viable manner). They can also consume a lot of electricity themselves, or require highly skilled technicians and engineers for day-to-day operation – a cadre that is simply in short supply in many countries.

Soils on land, sediments in the seas, and the plants that grow on them (and the self-living protists that today include brown algae, which form kelp forests) play a key role in the carbon and water cycles. Populations of certain plants and macroalgae, and consequently entire habitats, are sometimes heavily dependent on selected animal species, such as large and small herbivores. But not only that! For certain ecosystems, seed dispersers, or apex predators, are even more important, regulating the abundance of herbivores.

An example of the latter is, for example, the Kalan (sea otter), which is known from many textbooks to affect sea urchin populations, stopping the “apocalyptic” die-off of undersea forests and brown meadows. According to Schmitz and co-authors[3]a few select, ecophysiological groups of animal species, by restoring wildlife, could increase the potential for natural carbon sequestration by up to 250%! On a yearly basis, this would mean less anthropogenic greenhouse gas emissions by more than 6 Gt! Against the backdrop of 36.8 Gt released into the atmosphere in 2022. that’s quite a lot!

Ecosystem engineers: a few or many thousands?

Comments on this work published on some, Polish environmental portals tend to be highly simplistic and thus overly enthusiastic. The program theses of Schmitz and others, which are also hypotheses to be tested, are presented as finished results and conclusions. It is not uncommon to hint at only “a few species” capable of saving Mother Earth’s climate. Meanwhile, the original paper refers not to a few species, but to entire, sometimes very rich, internally diverse ecophysiological groups. In addition to selected ecosystem engineers that have been known for decades, such as the beaver, the aforementioned Kalan and the forest elephant, after all, we are talking about all marine plankton eaters, especially whale whales and peaceful fish. After all, there are thousands of species of the latter!

Key to success are keystone species

Like other rewilding practitioners, Schmitz et al[4] also emphasize the role of commonly known keystone (key) species groups:

• apex predators of land and sea: wolf and puma on land, sharks in the seas;
• large herbivores that are also ecosystem engineers: wildebeest, forest elephant, tapir, buffalo, muskox, caribou, wild horses, moose, vicuña, manatees and sea turtles;
• other ecosystem engineers: sea otters, beavers;
• oceanic plankton-eaters, mainly whalebone and marine still-feeding fish;
• Some seed dispersers, e.g.: fruit-eating bats, primates, beak-eating bats, as well as gridded beetles (chubby, pipits).

Pollinators are disappearing – including from scientific papers

Sometimes what is omitted from a given work can be just as important as the matters clearly discussed. From my perspective as a plant ecologist and urban meadowkeeper, it is incomprehensible and painful, for example, to overlook wild pollinators other than the honeybee (such as the melipona, the red-bellied wallflower and the bumblebee ) as a group crucial not only to wildlife, but also to agriculture.

The silence is all the more difficult to understand as new legislation is being dedicated to pollinators, and any day now a network of new Natura 2000 sites, connected by ecological corridors, so-called buzz lines, will be established across the European Union. As you can see, beneficial insects are disappearing not only from gardens and car windows, but also from the consciousness of some naturalists. Restoring the ecosystem services provided by wild pollinators is becoming one of the most important goals of modern rewilding.

From the perspective of aquatic ecosystems, flies of the buzzard family Syrphidae are a particularly important group of pollinators. The larvae of some species of these insects (63 out of 394 shown in Poland) mature in water, and can contribute significantly to the self-purification of standing waters[5]. Comprehensive protection of these flies is also receiving increasing attention in EU legislation[6].

Salon of the overlooked

It’s hard to deny that marine vertebrate filter feeders are important for wildlife and the economy. Nevertheless, it would also be worthwhile to appreciate the plankton-eaters of fresh and brackish waters, and among the omniocene species, the invertebrate plankton-eaters. All the more so since there is no shortage of umbrella and charismatic species whose protection serves to revild entire ecosystems like sturgeons.

Macrophytes, that is, plants of both vascular and bryophytes, as well as macroscopic algae (visible to the naked eye), should also be mentioned. They are an important group, both as living carbon sinks and as competitors to phytoplankton (including cyanobacteria), regulating composition and biomass in a given body of water. Macrophytes create habitats and feeding areas for many aquatic animals, as well as spawning grounds for many fish, known as “macrophytes. Phytophilous and phytolithophilous.

The biogeochemical cycle of carbon – like the cycles of circulation of other nutrients – could not close without the participation of saprotrophs that mineralize organic matter in bottom sediments and soils, often irreplaceable in the process of self-purification of water and restoration of soil fertility.

Averted view: is there such a thing as “keystone species”?

The results of the studies cited here and comments on the postulates of Schmitz and co-authors indicate that every component of the ecosystem is important. With successive publications, the category of “keystone/correlated species” grows, and thus blurs to include species that are less and less known to the layperson and less and less liked by non-naturalists. The concept of “keystone species” has its merits for science and for conservation administration. This is because it has improved communication between scientists and activists and policymakers and other professional groups.

It has contributed productively to saving a number of species, especially large vertebrates, and their entire ecosystems. It can still render invaluable services in selecting genres to create justifications and advertise a project amid dwindling resources of funds, time and qualified personnel. On the other hand, constantly expanding, it has undergone a certain amount of blurring and wear and tear. If we consider all species equally valuable, it makes no sense to distinguish some with the title of “keystone” and not others. Especially if they all interact equally strongly with each other in a given ecosystem. The optimal method of protecting individual populations and species turns out to be the protection of their entire environment.

In the article, I used, among other things. From the works:

[1] Nogués-Bravo D., Simberloff D., Rahbek C., Sanders N. J. (2016). Rewilding is the new Pandora’s box in conservation. Current Biology, 26(3), R87-R91.
[2] Schmitz O. J., Sylvén M., Atwood T. B., Bakker E. S., Berzaghi F., Brodie J. F., …, Ylänne H. (2023a). Trophic rewilding can expand natural climate solutions. Nature Climate Change, 1-10.
[3] Schmitz O. J., Sylvén M., Atwood T. B., Bakker E. S., Berzaghi F., Brodie J. F., …, Ylänne H. (2023a). Trophic rewilding can expand natural climate solutions. Nature Climate Change, 1-10.
Schmitz O. J., Sylvén M. (2023b). Animating the Carbon Cycle: How Wildlife Conservation Can Be a Key to Mitigate Climate Change. Environment: Science and Policy for Sustainable Development, 65(3), 5-17.
[4] Schmitz O. J., Sylvén M., Atwood T. B., Bakker E. S., Berzaghi F., Brodie J. F., …, Ylänne H. (2023a). Trophic rewilding can expand natural climate solutions. Nature Climate Change, 1-10.
Schmitz O. J., Sylvén M. (2023b). Animating the Carbon Cycle: How Wildlife Conservation Can Be a Key to Mitigate Climate Change. Environment: Science and Policy for Sustainable Development, 65(3), 5-17.
[5] Klukowska M. 2013. Buzzards Syprphidae. w: Tończyk G., Siciński J. (eds.) Key to the determination of benthic macroinvertebrates for the assessment of the ecological status of surface waters. Chief Inspectorate of Environmental Protection, Warsaw.
[6] Vujić A., Gilbert F., Flinn G., Englefield E., Ferreira C.C., …, Van de Meutter F., Veličković N., Vrba J. (2022). Pollinators on the edge: our European hoverflies. The European Red List of Hoverflies. European Commission, Brussels, Belgium.