A recent study published in the Journal of Paleoecology looked at the size of fish in the last interglacial period. It found that anchovies were less numerous. So, researchers conclude, that fish get less abundant when it’s warmer, but does it matter? Anchovies are near the base of the food chainA single thread in a food web illustrating the chain of animals that eat each other. At the base of the food chain are small high-energy (fast metabolism) animals and at the other end large low metabolism animals. An example would be whales eating krill that eat plankton that eat algae. Or lions that eat gazelles that eat grass. More and almost everything above depends on them. Commercial fisheries will certainly suffer but the greater and more worrying reality is absent from this paper. Snapshots in time are arbitrary, as the last interglacial, lasted for 13,000 years. We face a different and greater challenge.
There is no doubt this study is important. It adds more evidence to the fact that we are heading towards an ecosystem that can support less biomassThe weight of living organisms. Biomass can be measured in relation to the amount of carbon, the dry weight (with all moisture removed) or living weight. In general it can be used to describe the volume of energy that is contained inside systems, as the size of animals relates to their metabolism and therefore, how much energy they contain and More and therefore, fewer humans.
But the last interglacial lasted for millennia and the change in climate was only a tiny fluctuation in evolutionary time. Earth was still operating at a steady stable-state(of an ecosystem) where free surplus energy is minimised, where there is maximum entropy production and minimum waste. In such a system, there is expected to be relatively small fluctuations in atmospheric and other chemistry and where disruption or disturbance occurs, the resulting changes can be absorbed quickly by a succession of new plants and animals that enter to fill More. That’s to say, the Sun’s energyEnergy and nutrients are the same thing. Plants capture energy from the Sun and store it in chemicals, via the process of photosynthesis. The excess greenery and waste that plants create, contain chemicals that animals can eat, in order to build their own bodies and reproduce. When a chemical is used this way, we call it a nutrient. As we More could be absorbed into food chains and life go on, as normal. ‘Normal’ being a rate at which evolution, natural selection and cultural diversification was sufficient to maintain a diversity of species. This is the sole mechanism that makes the planet habitable for humans.
There was no mass extinctionAnimal life hasn't existed for very long on planet Earth. In the last 500 million years, there have been five mass extinctions, defined as events that wiped out at least 75% of animal life. The Devonian mass extinction is considered to have been caused by the rise of plants on land, which polluted the oceans in the absence of animals. More. EcosystemsHow ecosystems function An ecosystem is a community of lifeforms that interact in such an optimal way that how ecosystems function best, is when all components (including humans and other animals) can persist and live alongside each other for the longest time possible. Ecosystems are fuelled by the energy created by plants (primary producers) that convert the Sun's heat energy More were relatively stable. Humans survived this period.
Our next thirty years is a very different ‘kettle of fish’ if you’ll excuse the metaphor ; )
We are not heading for 2ºC warming
I keep hearing scientists talk this way but it’s misleading. In the modern day we have two problems: the release of fossil fuel and the extinction of animal life.
We aren’t simply heading for 2ºC warming, we are heading for wholesale destabilisation of ecosystems. It just so happens that physics dictates this to be in a warming direction but that’s arbitrary. It’s a correlation but it is not the thing we need to be concerned about.
The paper’s abstract says:
‘These small fish species are more difficult to harvest and are less palatable than anchovies, indicating that our rapidly warming world poses a threat to the global fish supply.’
If we were just heading for a reduction in fish numbers that would be manageable as we could adapt. 120,000 years ago anchovies were doing okay. Their numbers weren’t as high as they are today, but they survived the interglacial period, as did we.
The real problem we face now is that anchovies, like humans, will have to survive a period of intensive ecosystem instability. Numbers and distribution of fish won’t just decline, they could become so unpredictable, as to become dysfunctional.
It’s about chaos not warming
Let’s go back to the question. Fish get less abundant when it’s warmer, but does it matter? The answer is, of course, yes – if those fish are the base of a food chain.
Boris Worm, quoted in Mongabay says:
“We cannot expect fish harvest to remain the same under climate change, and need to use our dwindling supply more cautiously, allowing for wider margins of error”.
But this presumption only holds if the margin of error relates to numbers of fish. It assumes that warmer ecosystems carry fewer fish. This might have been true 120,000 years ago before human capital exceeded natural capital. Also, over over timescales, of tens of thousands of years. But today’s situation is completely different.
First, the change is so rapid, that there are already huge fluctuations in extremes of temperature and weather (which links directly to the ocean). Second, we have removed a huge amount of wild animal biomass from the land and ocean which was responsible for maintaining stable ecosystems.
The paper forecasts declining fish stock without making any prediction about the impending chaos(Of energy and ecosystems). Ecosystems are thermodynamically driven. Disorder occurs when energy dissipates and becomes more chaotic. For example, the release of hot air into the atmosphere results in that energy is freer to disperse (maximum entropy). The opposite is true when energy is locked into biological processes, when it is stored inside molecules (minimum entropy). Stability in ecosystems occurs More in ecosystem function(Of an ecosystem). A subset of ecosystem processes and structures, where the ecosystem does something that provides an ecosystem service of value to people. More. It compares a time when climate systems were biodiversity-linked, with a time now, where they are not.
Our impending problem is the reduction in ecosystem stability inherent in our burning of fossil fuels and killing of wildlife. This paper, like so many ecological studies, doesn’t seem to even acknowledge this overarching paradigm. It takes a complex system and distils it into a single linear narrative that ends up with the conclusion: we will need to eat fewer fish.
