All Creatures Great and Small

There often seems to be a juxtaposition between the concerns of professional conservationists and those of the general public when it comes to the conservation of species. During my undergraduate degree, I had many lectures that highlighted the distribution of species between different taxa. The majority of recorded species on earth are insects, and the order Coleoptera (beetles) alone contributes more than 350,000 species to the diversity of life. This fact lead to an infamous and possibly apocryphal story about J.B.S. Haldane, one of the founders of population genetics. When asked what his studies of creation had allowed him to conclude about the nature of a Creator, he is said to have answered ‘An inordinate fondness for beetles’.

Inordinate fondness for beetles

In comparison, there are a grand total of around 15,500 species of mammals and birds. Yet these groups command the majority of conservation money and, importantly, public attention and sympathy. This is where the disconnect lies. Ecosystems, their functioning and their upkeep depend on the roles that species play. In a 2008 study children were asked to draw their ideal rainforest and the result is shown in the species scape. The size of each animal represents the frequency with which each taxa was drawn by the children. The picture directly below shows the relative contribution of each taxa shown to the biomass of a rainforest. As it can be clearly seen, children hugely over-represent vertebrates and under-represent insects and worms.

Species scape

Snaddon,Turner & Foster. (2008)

The authors conclude by saying that ‘Scientists and naturalists must continue to emphasise the diversity and functional importance of lesser-known taxa through public communication and outdoor events to aid invertebrate conservation’. But I question how effective this approach can be. Whilst to some, insects are the most fascinating things, to the great majority of people a tiger, lion or elephant will win over every time. In the quest to emphasize the importance of invertebrates to the integrity of ecosystems, there is a tendency to brush over the functional importance of vertebrates. After all vertebrates get the vast majority of the conservation spending already so their functional importance doesn’t need to be highlighted to the same extent.

In the last few years, research has pointed out just how important megafauna are to ecosystems, and the vital roles that they play. In fact, all the ecosystem research we have ever carried out may be done in systems that lack some fundamental processes that megafauna would have been undertaking up to 13,000 years ago. It seems like the extinction Pleistocene megafauna removed much of the capability of ecosystems to spread nutrients across landscapes. This has given us a less fertile planet overall and the presence of these large animals may have mitigated the oversupply of nutrients in eutrophic systems and the undersupply of nutrients in others such as phosphorous in Amazonia. We can also see the real time effects of the exclusion or introduction of extant species. Apex consumers play key and often overlooked roles in ecosystems. Removing these, a process known as ‘trophic downgrading’ has cascading effects that ripple through the trophic web of a system, having unexpected but often deeply important effects. The extirpation of sea otters results in the wholescale destruction of kelp forests, the introduction of arctic foxes onto islands turns grasslands into tundra and the removal of coyotes can cause collapses in small vertebrate populations due to mesopredator release. It is obvious then that large, charismatic animals that capture the public’s imagination do play key roles in the maintenance of ecosystems that shouldn’t be overlooked.

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Sea otters show that animals can be cute and central to ecosystem function.Credit: Chuck Abbe

Large animals are important to ecosystems in ways that invertebrates struggle to be. This can largely be attributed to their size itself. The graph below shows the relationship between body size and range length, large animals move around over larger distances than smaller ones.

Graph

The relationship between an animal’s mass and how far it moves. Wolf et al. 2013

This makes these large animals effective mobile links. These are species that provide ecosystem services by moving between and connecting habitats and ecosystems. Mobile links increase ecosystem resilience (the ability of ecosystems to withstand disturbance) and memory (the ability of ecosystems to reorganise after disturbance). As an example, imagine a severe storm fells an area of forest in the Amazon. Rainfall then erodes the soil and leaches out the nutrients. It may then be a struggle for the forest to regrow in this area. Large herbivores are able to enter the system from outside and act as external ecological memory. Their dung and carcasses reintroduce nutrients to the soil and help the forest to regrow. In an uncertain future of ongoing land conversion and more frequent extreme weather events, ecological memory and therefore large vertebrates may be crucial to the persistence of ecosystmes.

Like in any industry, branding is key in conservation. We must face the fact that in general it is much easier to sell the fluffy, the feathery and the large than it is to sell the creepy, the slimy and the small. How then to reconcile the need to conserve those that fall into the latter groups with the easier task of selling the conservation of those that fall into the former ones? In my opinion the answer lies in utilising the captivating mammals and birds to act as umbrella species. However, care is needed in this approach. If we focus too much on these flagships, their conservation can be used as an excuse for trashing the rest of the system. This was attempted in the case of the northern-spotted owl when the forestry industry proposed feeding the owl to compensate for the loss of forest. In this way, the species doesn’t act as an umbrella, rather the opposite in fact.

cartoon

Credit: Rohan Chakravarty

To ensure that protecting umbrella species really does protect the whole ecosystem, we must emphasise the functionalist approach. Megafauna fulfil key functions and we must allow them to do so in intact ecosystems. The solution to protecting the umbrella species concept against misinterpretation? Rewilding. If properly applied, this approach can be a win-win-win. The public get to see active conservation of the large and fluffies which can be used to raise funds and awareness, the functionalists and wildness-lovers get to see new areas which they can appreciate, and the entomologists and champions of the invertebrates get to see ecosystems in which their unsung heroes can thrive. This isn’t to say that we shouldn’t be trying to educate people about the importance of insects and try and sell the wonder of them. After all, who can look at a spider’s web or termite nest and not gawp? But conservation of these species will always be a much harder sell just because of human nature. Alongside this approach, rewilding gives us an opportunity to protect this oft-overlooked diversity.

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