Zara Hossain-Ibrahim – Year 13 Student
Zara Hossain-Ibrahim is one of the winners of Peterhouse’s Kelvin Science Prize in 2019. The standard of entries was really high but the judges felt that her essay stood out for its clarity of argument, stylish prose, level of research and originality of thought. This commendation puts her in the top 10 out of over 200 entries. Peterhouse Judging Panel
British ecosystems have become static and the variety of species has declined. The reintroduction of wolves into Britain would be a step towards restoring species richness by triggering trophic cascades and increasing spatial variation of habitats within ecosystems. This would increase the evolutionary potential of organisms and potentially improve their ability to adapt to climate change.
During the Arboreal and Atlantic periods, Britain was almost universally forested. However, in England, the average woodland cover is now only 12%. This is largely the result of agricultural practices, urban spread and shooting estates. Thousands of acres in the Scottish Highlands are used for deer stalking; the deer are kept at unnaturally high densities as they are fed in the winter and their predator populations are controlled. Furthermore, it is difficult to establish new habitats as the deer eat the nutritious saplings and prevent the climax community establishing. The sheep/hill farming industry has led to an increase in agricultural land as farmers are incentivised to maintain clear land, devoid of ‘ineligible features,’ such as trees, ponds and wide hedges. This has resulted in land devoid of vegetation. The shifting baseline syndrome, first put forward by Daniel Pauley suggests that conservation ethos has idealised an image of biodiversity far more limited than what had prevailed many generations back. Monocultures have developed due to the burning and felling of vegetation, only allowing a limited species to survive given the lack of cover. The resulting ecosystem is stagnant and requires extensive intervention to maintain. Monbiot cited a study in the Cairngorms, which showed that wooded habitats were thirteen times richer in nationally important species than moorland areas, and contained almost all endemic British species. This highlights the biodiversity that could develop through rewilding, as forests would be allowed to recover allowing a range of species to repopulate. The unpredictability of such interactions allows ecological interactions to occur naturally and bring back diversity in an organic manner not constrained by a human belief in stewardship, which has only served to promote genetically constrained environments such as heather moorland and rough grassland where only resilient species such as the red grouse and skylark can survive.
By reintroducing wolves, the population of deer in Scotland would be suppressed. The wolves would create a ‘landscape of fear’ meaning areas that the deer could occupy would also be controlled, as they avoid open spaces that would leave them vulnerable to attack. This means that certain areas would undergo heavy grazing while others would be released: a habitat mosaic. The trees would be allowed to grow, meaning the ecosystem could accommodate more species due to the greater variety of microhabitats. The species diversity would also increase due to the formation of unique niches that would incorporate the extreme conditions needed to sustain the variety of life, organisms requiring controlled environments of humidity and temperature would be able to thrive in habitats provided by deadwood. The return of wolves would therefore trigger a trophic cascade, as they would reduce the abundance of their prey which would then allow the prey’s food source to prosper. Aspen (Populus tremula), which is currently rare in the Highlands, would return as their saplings could grow. With it, nesting opportunities for woodpecker, species of lichen, and insect would return. Further spatial heterogeneity would be established as the wolves would create unphased disturbances when, for example, abandoning carcasses of their prey. This would provide carrion for scavengers and any of the remaining body fluid would seep into the soil, providing a competitor-free and nutrient rich area. This constantly altering patchwork of habitats would mean a dynamic ecosystem which would be capable of supporting an array of species. Therefore rewilding helps to increase trophic diversity, by widening and lengthening the food web; thus enabling more producers and consumers to populate each ecosystem.
Evidence that such a dramatic change would occur is most obviously seen in the reintroduction of wolves to Yellowstone, 1995. The population of red deer was culled and the areas they occupied reduced. The height of trees on the banksides quintupled and the number of beaver colonies rose by 24 between 1996 and 2009. As Keystone Species, the beaver and wolf both have a larger impact on ecosystems than their biomass; this impact creates environments other species need to survive. This meant that when beavers began to return in Yellowstone, the environments created by their dams and burrows allowed otters, water vole and amphibians to return. Creation of the dams meant that faecal bacteria was filtered out, preventing the spread of disease, and flooding was prevented downstream due to the retention of water. Furthermore, phosphates, nitrates and pesticides released by farmers wouldn’t flow downstream, allowing vegetation and wildlife to grow without the toxicity they create. This has also reduced soil leaching, leading to a stronger baseline for the ecosystem to thrive from. Wolves through predation can similarly alter the course of the river through stabilisation of the river banks by vegetation and tree roots. Formation of small wetlands and boggy marshes have allowed further species to grow, enhancing the opportunity for organisms to rebuild broken strands of the food webs that once existed. This alteration of vegetation also prevented flooding due to steady release of water into the river, meaning a lower discharge and longer lag time.
The wolves would also enable more species to enter the ecosystem as their aggregative behaviour could lead to the coexistence of competing species without the need for niche differentiation. The development of a heterogeneous environment may have a stabilising effect on ecological interactions. In an experiment using a parasitoid (wasp) and two caterpillar hosts, Bonsall and Hassel (1997), where they first allowed the parasitoid to pass between host species, but segregated the caterpillars, thus avoiding interspecific competition over resources, both populations diminished towards a stable equilibrium. However, when the system was again run with both host species in the same space, the parasitoid reduced the population of the species with the lower intrinsic rate of increase. This shows that one of the hosts is able to survive by adapting a behavioural pattern different or niche enough to the other host. This suggests that the reintroduction of wolves may lead to adaptation and the underlying genetic variation needed for this ensures the resilience and dynamism needed for an ecosystem to survive under climate change. The importance of genetic variation and adaptability is highlighted in 1970 where the USA lost 15% of its corn crop to a single fungus, showing monocultures can lead to land becoming barren. In order to prevent this, the rewilding of species would allow biodiversity and ensure only fitter members of a population would survive, leading to a genetically stronger population as beneficial alleles would be inherited.
Furthermore, the reintroduction of wolves will affect soil type by changing nutrient composition. A greater variety of life will ensure breakdown of more organic material into soil, leaving a fertile and amorphous humus. This will help to retain soil nutrients in a form that will become gradually available to wildlife. The alteration of mineral composition is important as it affects water retention capability and drainage. Such factors will lead to a greater biodiversity of plants or ‘producers’ facilitating a wider range of consumers, therefore widening trophic diversity.
To conclude, rewilding would be an effective way to achieve the mass restoration of ecosystems. There are no ecological constraints preventing the reintroduction of wolves, and it has been completed successfully across Europe, and famously in Yellowstone. The restoration of such a keystone predator would indeed restore trophic diversity and ecological balance. By allowing ecosystems to flourish with little input from such potentially misguided stewardship such as ‘conservational burning’ in Dartmoor, complex habitats will return with emergent adaptive qualities, in contrast to the current simple system of predictable outputs and inputs. Therefore, in order to restore British ecosystems and allow them to grow largely independently, with species able to enact their natural behaviour, the rewilding of species such as the wolf should occur.
J. Silvertown (2010), Fragile Web What Next For Nature?- Natural History Museum.
M. Begon, C.R Townsend, J.L. Harper (2006), Fourth edition, Ecology From Individuals To Ecosystems- Blackwell Publishing Ltd.
C.J Clegg, D.G Mackean (2000), Second edition Advanced Biology, Principles & Applications- John Murray
G. Monbiot (2004), Feral, Rewilding The Land, The Sea and Human Life- University of Chicago Press
Rewilding George Monbiot talk:- Hosted by Sustainable Earth Institute, Plymouth university: https://www.youtube.com/watch?v=ZHw8yiHD4Iw&t=883s