Home » We’re in the midst of an ecosystem brain drain

We’re in the midst of an ecosystem brain drain

by simon

A paper just published in the journal Nature [1] has reviewed hundreds of studies on the impact of humans on the movement of birds, mammals, reptiles, amphibians, fish and arthropods. The study found that in two-thirds of cases, animals were having to move up to 70% further to find food. Disturbance from recreation and hunting, had stronger impacts on animal movement than habitat modification, such as logging and agriculture. Not knowing where to find food, means we are in the midst of an ecosystem brain drain.

If you’re an animal in a pristine landscape, you move places you know where to find food and while you’re there, you prune the vegetation and lightly fertilise it, so it reappears strongly next year when you return.

As we’ve discussed elsewhere in this blog, migration is really important for nutrient transfer and it’s the trait that sets animals apart from all other lifeforms. It’s also one of the principle reasons we need other animals –human beings aren’t very mobile. We can’t walk more than a short distance every day and we no longer act as as hunter-gatherers, so even our short migrations to moderate resources like meat and fruit, has been replaced with car-trips to the supermarket.

It’s the reason animals are critical to stabilising ecosystems and enabling human life support. Migration happens for a reason and it’s not always on a massive scale. The daily movements of insects to and from flowers or the vertical movement of lantern fish from the deep ocean at night, are all migrations.

Think about wild animals as awesome remote sensing machines, but ones that self-replicate and learn for millennia, through a constant cycle of life and death. Moreover, they both take from the environment and give back to it. If you’re an animal in a pristine landscape, you move places you know where to find food and while you’re there, you prune the vegetation and lightly fertilise it, so it reappears strongly next year when you return.

Animals knowing both where to find food, being part of cultivating it and being able to move between seasonal patches, is what makes ecosystems stable and diverse. Animals are coupled to the process being both givers and takers but the knowledge they need, is based on an evolved survival strategy.

ecosystem brain drain
Dugongs will swim hundreds of kilometres between patches and have a profound impact on their environment, even reducing seagrass growth by half but this is good. Dugongs can remove the majority of seagrass shoots and three-quarters of growth from four centimetres below ground but it only takes a few months to recover and the seagrass bounces back richer, with carbon stored overall.

When we interfere with those processes and restructure them by building roads, cutting down forest or polluting habitat, we are not only impacting on the animals’ survival, we’re also impacting on the ecological functioning of the landscape. It’s this function that delivers biodiversity, meaning all the things we need for a habitable Earth. We need to be aware that our impact on animals will come full circle and affect our own survival, if we allow it to get out of control.

The guidance systems animals use for nutrition are based on information they store in their brains about where and when they expect to find food. Some of this is physical and predetermined and some is learnt. You can break the process of ecosystem stability by either altering their environment or removing animals themselves. This is why it s harder to rehabilitate ecosystems, the longer animals have been absent (see Cingolani, 2005 in the following link).

A paper published in the journal Science compared the movements of real reintroduced, radio-collared bighorn sheep in North America, to a theoretical model they created. The model had one herd doing random movement and another that knew precisely where green vegetation occurred (the omniscient herd). Researcher Matthew Kauffman from the University of Wyoming described the results online in The Atlantic:

Some of the recently translocated herds tracked the green wave no better than the ones that wandered randomly,” says Brett Jesmer, who led the work. The older herds did far better—“not as well as the omniscient ones, but closer,” he says.

In other words, these animals lose their local cultural knowledge of where to find food, if they are removed from the land. Between 65 – 100% of wild bighorn sheep migrate but fewer than 9% in translocated herds. The only ones that did better, were translocated into existing herds and able to pick up some of the cultural knowledge.

Newly-reintroduced animals begin, as you’d expect, wandering aimlessly looking for food. The scientists found that only after “several decades, newly established herds were better able to track the emergence of vegetation in the environment”. In Chernobyl, a herd of domestic cows have been found to have rediscovered their wildness and started behaving socially, like the herds of wild turs that they are related to. During COVID, animals moved back into cities very quickly, showing us that our mere presence is enough to force them away. Perhaps this is a hopeful sign that animals can step in and start to rebuild ecosystems for us quite quickly.

It makes me wonder though, how long it would take for animals to create the level of knowledge needed, not only to start redeveloping migration patterns but stabilise ecosystems? The “omniscient” herds described in the scientists’ models (above) are likely to be similar to herds in a pristine ecosystem.

It isn’t the mere presence of animals that creates life support, it’s their connection to country and this information process can take an extraordinarily long time to recreate, especially when the supporting environment is in a state of chaos.

You see, if we were dealing with a stable landscape and reintroducing animals, that would be simple– unfortunately, this is largely how we currently think about animal conservation.

We don’t realise that we’re dealing with a landscape that is destabilised because animals were removed and we are imposing other impacts as well, such as fossil-fuel-driven climate change. We have two systems that have to reach alignment, both of which are in a state of chaos and can only ultimately be reformed by adding animals and letting natural processes happen.

As a world, we haven’t yet worked out that animals are this essential for a habitable Earth and the biodiversity processes they drive (that deliver clean water, food security and stable climate), are the consequence of the interaction they have with the landscape.

  1. Doherty, T.S., Hays, G.C. & Driscoll, D.A. Human disturbance causes widespread disruption of animal movement. Nat Ecol Evol (2021). https://doi.org/10.1038/s41559-020-01380-1 https://www.nature.com/articles/s41559-020-01380-1
  2. Jesmer, Brett & Merkle, Jerod & Goheen, Jacob & Aikens, Ellen & Beck, Jeffrey & Courtemanch, Alyson & Hurley, Mark & McWhirter, Douglas & Miyasaki, Hollie & Monteith, Kevin & Kauffman, Matthew. (2018). Is ungulate migration culturally transmitted? Evidence of social learning from translocated animals. Science. 361. 1023-1025. 10.1126/science.aat0985.

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