How predatory arachnids absorb carbon in grassland

The environmental newspaper Mongabay published a piece titled ‘Animating the Carbon Cycle: Earth’s animals vital allies in CO2 storage.’ It’s long been known animals are essential for ecosystem vitality. But Professor Oswald Schmitz at the Yale School of the Environment tells me that: ‘I have been trying to get the scientific community to pay attention for a decade or more.’ In his work Schmitz describes how predatory arachnids absorb carbon in grassland.

There are so many paradoxes in ecological science. I have a love-hate relationship with them. I love them because they are so peculiar and hate them because they create so much misinterpretation – even among scientists.

For instance, there is the perennial idea that predators outcompete prey. Wrong. Without predators prey go extinct.

Spiders and carbon absorption

When it comes to carbon we also think it’s all bad. But we’re made from carbon. Carbon is also one of the most important elements that carries 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 around the Earth.

What Schmitz has discovered is the importance of ‘active’ predators at all scales from sharks to small creatures like spiders.

In a 2017 study in the journal Ecology his team showed that ‘the amount of soil [Carbon] retention within a field should increase with the proportion of active hunting predators comprising the aboveground community of active hunting and sit-and-wait predators.’

By active, they mean jumping spiders and peacock spiders – ones that hunt rather than sit and wait at their web.

The results were really significant. Forty-one per cent of the variation in carbon was explained by this phenomenon. While plant 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, insect and soil arthropod community composition, land use development, field age, and soil texture had little effect.

As I described in my article ‘Spiders weave the threads of a new beginning’, this group of creatures is incredibly powerful for rebuilding broken 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.  

How it works

When predators are imposed on a system they create gaps in the structure. They apply pressure on herbivores and this actually creates a market-gap for more species. This same cascading diversification of pressures influences plants too. They bounce back stronger and more nutritious (richer in energy). Add in birds and mammals and you have a truly extraordinary and powerful system.

Without predators, this whole system becomes stagnant and collapses.

Grasslands are thousands of times more species-rich on a small scale, than rainforests and in the Czech Republic can have 44 species for every 25 x 25 cm – that’s 7,500 times more species-rich than a hectare of the Ecuadorian rainforest. 

Why is this important or controversial?

When you introduce animals into a system the increased carbon is initially amplified and in excess. This is before the other creatures have moved in to rebuild the structures. Scientists tend to measure ‘excess’ … because what isn’t in excess is practically invisible and immeasurable. Excess carbon can mean a system is broken but it can also mean a system is being rebuilt. This can be seen as a risk by those who don’t understand the role of animals in ecosystem stability.

But nature-based solutions to the biodiversity crisis are messy. They are also the only way to recreate a habitable planet and work faster than any other method. Simply leaving nature alone creates the quickest outcomes but that means going though ‘the dip’ as marketing expert Seth Godin explains. (There are strong similarities between all elements of human society and how ecosystems work, something you’ll discover if you read my book Wildlife in the Balance).

So, while excess carbon represents a ‘risk’ among climate-thinkers, we also need carbon concentrated at levels that deliver our food. In the end, we absorb more carbon into food systems where we need it. Remember, the amount of carbon on Earth hasn’t changed, only the distribution of it from where it is useful, to where it is not.

We are big animals. If we allow predators – including spiders – to go extinct, we kill ourselves. Our ecosystems become uninhabitable.

The only way to guarantee this isn’t going to happen is to allow animals to increase carbon in ecosystems. If that means helping spiders exist, it means using no pesticides. As each time we do that, we kill off the soil-creating mechanisms that we rely on for food.