Rewilding Ibera
What is next and how far could we go?
One of the largest and most ambitious rewilding projects currently being undertaken is in the Ibera wetlands of Corrientes province, north-eastern Argentina. The Ibera Provincial Reserve is massive, with a land cover of over thirteen thousand kilometres (five thousand square miles), and contains many different types of habitat in addition to its sizeable wetlands. The reserve has gained attention recently for its very progressive view towards the reintroduction of large animals. Currently the organization is involved in the ongoing reintroduction of seven species, the planning of at least one other, and the reinforcement of two or three more. This sort of consecutive introduction is basically unheard of in areas outside of Africa. It represents a very exciting opportunity to reconstruct the southern end of the Humid Chaco ecosystem and to develop a rich and vibrant ecotourism industry in the region. However, I would be very interested to explore potential reintroductions which have not yet been proposed, or at least not yet published. This will be a purely hypothetical exercise and I would stress that I have no affiliation to the project, but the sheer number of possibilities for the area is very intriguing and I would like to share my thoughts on the matter.
First, a summary of ongoing introductions to the reserve. The current list is as follows: green-winged macaw (Ara chloropterus), giant anteater (Myrmecophaga tridactyla), pampas deer (Ozotoceros bezoarticus), jaguar (Panthera onca), collared peccary (Pecari tajacu), giant otter (Pteronura brasiliensis), and lowland tapir (Tapirus terrestris). Bolstering projects with red-legged seriema (Cariama cristata), maned wolf (Chrysocyon brachyurus), and possibly lesser anteater (Tamandua tetradactyla) are also occurring, and a reintroduction project involving the bare-faced curassow (Crax fasciolata) is currently in the works, though I do not know if any acquisitions have been made yet. What I notice for all of these species is that without exception they are large, ecologically powerful species (especially in the cases of the jaguar and tapir), which play important roles in seed-dispersal, grazing dynamics, and/or top-down regulation, and which might be dubbed keystone species, meaning they have a disproportionate effect on their ecosystem when compared with other animals. The species they have started with seem ideal, and will do much to restore ecosystems dynamics to the area, potentially attracting smaller species which may also have been extirpated.
I find the curassow particularly interesting as there is not, it would seem, any actual records of the species in the area of the Ibera wetlands. This is not to say they should not be introduced, in fact I feel quite the opposite. It is a rather progressive move to consider introduction of a species not based exactly on previous occurrence, but on its ecological role and its general history in the larger ecoregion. Curassows probably did inhabit Ibera at one point, and the lack of historical records probably reflects their general ambiguity amongst colonial settlers who, when they did record the species they encountered, were more likely to take note of more visually obvious creatures like parrots and tapirs. When you consider that currasows:
- Are certainly native to the Humid Chaco ecoregion and proper habitat seems quite readily available in Ibera
- Are vulnerable and could use good-quality protected habitat
- Are an important seed-dispersing species which would contribute to biodiversity
then the curassow seems rather an ideal candidate. Similar logic might be used to justify the introduction of other species with no surviving records from the area. I will be discussing several such species which might be considered.
The first group I would like to explore is the Artiodactyla, or even-toed ungulates. On top of the pampas deer and collared peccary being reintroduced, there are marsh deer (Blastocerus dicotomus) and grey brocket (Mazama gouazoubira) already present in Ibera, and there may have been two additional species present in pre-colonial times. These are the red brocket (Mazama americana) and the white-lipped peccary (Tayassu pecari). Both are reported to have been present in Corrientes province at some point, though not specifically in Ibera as far as I can determine. Both are common elsewhere in the Humid Chaco, and would potentially be useful in restoring herbivory dynamics, as well as providing additional prey species for growing populations of native carnivores. Some habitat assessment may be necessary to determine if the reserve could support these two species. Adequate forest cover for red brocket may be lacking in the area, which might explain their current absence, but white-lipped peccary are far more flexible with their habitat preferences and would almost certainly thrive in Ibera if given the opportunity.
Primates are another angle. Currently there is only one species present in Ibera, the black howler monkey (Alouatta caraya), but the Humid Chaco supports two other species which may have had wider distributions in the past: the hooded capuchin monkey (Sapajus cay) and the southern night monkey (Aotus azarae). The capuchin in particular is likely to have occurred further south in historic times, with colonial observations of “Cebus apella” from Entre Rios, even further south than Corrientes, probably being referable to this species, which was previously considered a subspecies of the tufted capuchin, Sapajus apella, formerly Cebus apella. Records of night monkeys are lacking, but their current distribution spreads well into other areas of the Humid Chaco in Paraguay and elsewhere in Argentina. Both species would likely require some degree of forest cover, but to what extent is unknown. Both would inevitably drive ecotourism, as monkeys are near-universally considered charismatic. (After all, everyone likes monkeys!)
Large caviomorph rodents are already common in the form of the greater capybara (Hydrochoeris hydrochaeris), plains vizcacha (Lagostomus maximus), and the Brazilian cavy (Cavia aperea). Pacas (Cuniculus paca) and agoutis (Dasyptocta azarae) are occasionally spotted in Corrientes and are populous in other parts of the ecoregion. Both are important herbivores and seed distributors, filling a role similar to that of muntjac and chevrotains in Asia. They are also common prey species for numerous different carnivores. Porcupines might also have been present in the area at one point, with two species (Coendou prehensilis and C. spinosus) ranging into various parts of the ecoregion. The only native lagomorph is the tapeti (Sylvilagus brasiliensis), a small cottontail rabbit that appears to have been extirpated from the province.
Cingulates are common in the form of nine-banded armadillos (Dasypus novemcinctus), long-nosed armadillos (Dasypus hybridus), seven-banded armadillos (Dasypus septemcinctus), six-banded armadillos (Euphractus sexcinctus), and naked-tail armadillos (Cabassous tatouay). Armadillos are key components of South American ecosystems, contributing greatly to invertebrate control and soil disturbance. The reintroduction of two larger armadillo species, the hairy armadillo (Chaetophractus villosus) and the giant armadillo (Priodontes maximus), would stimulate these processes further. Neither has extensive records in the province, but both are found elsewhere in the Humid Chaco and may well have been present at one point. The giant armadillo in particular has lost much of its distribution in the humid areas of Paraguay and Argentina, and its Vulnerable status would suggest that introduction to new protected areas might be advisable. The giant armadillo is considered an ecosystem engineer due to its habit of creating massive burrows used by multiple other species. Easily the largest of the cingulates, it would also be a draw for tourism.
The reintroduction of jaguars is a crucial step in the reestablishment of top-down predation to the reserve, especially since they may help to control invasive species like wild boar (Sus scrofa) and chital deer (Axis axis), but there are other large felids which may require reintroduction and/or reinforcement. Currently the only established felids are Geoffroy’s cat (Leopardus geoffroi) and the jaguarundi (Herpailurus yagouroundi), with ocelots (Leopardis pardalis), pampas cat (Leopardus colocolo), and margay (Leopardus wiedii) being much rarer, if present at all. Pumas (Puma concolor) are sighted occasionally on the reserve, but do not appear to have a significant breeding population, the formation of which would also be crucial to the re-establishment of regulatory processes. While there is extensive overlap in diet between jaguars and pumas, the two do coexist in many areas of the Americas, and will enforce niche separation through differences in prey and habitat preference. Margay may be limited in their colonization of the wetlands by tree cover, but ocelots and pampas cat would likely do very well in Ibera, especially if large rodents and rabbits become more common and diverse.
(Note — This article was originally written in 2019, a project to reintroduce/reinforce ocelots in Ibera has since begun.)
There are five very large reptiles which are already established in Ibera. Two members of the alligator family, the broad-snouted caiman (Caiman latirostris) and the yacare caiman (Caiman yacare), as well as the yellow anaconda (Eunectes notaeus), the common boa (Boa constrictor), and the black-and-white tegu lizard (Salavator merianae). All of these are important predators in the region, especially in the absence of jaguars and pumas. There have, as yet, been no reptile introductions in Ibera, but I would suggest that one particular group could use some attention: turtles.
Currently the only species present are the side-necked turtle (Phrynops hilarii) and possibly the toad-headed turtle (Mesoclemmys vanderhaegei) and the slider (Trachemys dorbigni). There are two other aquatic species found in the surrounding area, which might benefit from a range expansion: the snake-necked turtle (Hydromedusa tectifera) and the swamp turtle (Acanthochelys pallidipectoris), with the latter being considered endangered. Tortoises may also have an important role to play in the ecosystem we are trying to reconstruct, and are certainly charismatic animals, but it is unclear if they were ever present in Ibera. It seems likely, as there are tortoises to the west and south, and to the north and east, and it would be odd if only this small patch in the middle were tortoise-free.
Other parts of the Humid Chaco host the red-footed tortoise (Chelonoidis carbonaria), and it is likely that Ibera could start its own population of this species, which is considered vulnerable in the wild but which is rather common in captivity. Unlike the related yellow-footed tortoise (Chelonoidis denticulata), the red-footed tortoise is comfortable in open habitats with low tree density, and unlike the Chacoan tortoise (Chelonoidis chilensis), it does well in humid environments with lots of water, making it likely the ideal choice. Tortoises are important grazers and seed distributors, and are easy to breed and manage.
The only remaining group to be discussed in this article is a rather broad one: birds. There is already a huge diversity of birds in Ibera, including a population of one of the largest birds on Earth, the ostrich-like rhea (Rhea americana). In addition to the macaws and curassows that are already in the process of reintroduction, I can think of only one species that seems rather conspicuously absent, the king vulture (Sarcorhamphus papa). Sometimes called the jungle condor, for good reason, king vultures are a good indicator for healthy populations of megafauna, as they rely on the presence of carrion for their survival. The reserve already has populations of black vultures (Coragyps atratus), turkey vultures (Cathartes aura), and yellow-headed vultures (Cathartes burrovianus), and research suggests that king vultures are beneficial to these species, since they can tear open carcasses that these smaller birds cannot, allowing them better access to food.
Overall there remain many interesting potential introductions for Ibera, and it will be fascinating to see how they progress over the next few decades. They may come up with potential introductions that I have missed (or someone else might), or they may already have unpublished plans for some of the aforementioned species. I also think Ibera, or the Humid Chaco in general, could eventually be an ideal experimentation site for the use of prehistoric baselines, with the understanding that human influence on the ecosystem goes back much further than typically thought. I have some ideas for what species might be used in such an experiment, but that is perhaps a topic for another article, and there is much work to be done first.
The Ibera wetlands have the potential to be an ecotourism destination comparable to parks in other humid semi-tropical climates, such as Chitwan in Nepal, Kaziranga in India, or Kafue in Zambia. There are certainly parallels to be made between the fauna of these areas, minus the megafauna (but more on that another time). There are plenty of charismatic species present which will do much to attract guests to the area, even before reintroductions. In addition to the larger species discussed, diversity of small mammals, birds, and reptiles is also very high, allowing for many sighting opportunities. Ecotourism-based development of this region would likely be very beneficial to the local community, creating jobs and income. Hopefully, increased visitation would also streamline the process of getting there, with more flight and transport options becoming available both to people within Argentina and abroad. I myself would very much like to visit Ibera one day, and I hope it becomes the world-class ecotourism destination it has the potential to be.
Rhys Lemoine is a PhD Researcher at BIOCHANGE, Aarhus University. Follow him on Twitter @LemoineRhys.
