Biomass: Humans 0.01% of life but destroyed 83% of wild mammals

[Jamie in Chile]

An interesting study has been published this week (Monday) in Proceedings of the National Academy of Sciences of the United States of America. The work was led by Prof Ron Milo, at the Weizmann Institute of Science in Israel, and the other authors were Yinon M. Bar-On and Rob Phillips.

The study can be found here: The biomass distribution on Earth and it is reasonably easy to read as scientific studies go: at least the abstract and results are worth a look. The Guardian has a more reader friendly write up of it with graphics: Humans just 0.01% of all life but have destroyed 83% of wild mammals – study I also borrowed their headline.

60% of all mammals on Earth are said to be livestock, mostly cattle and pigs, 36% are human and just 4% are wild animals.

The following is the relative biomass - using a unit of gigatonnes of carbon. So the statistics below are by weight/mass rather than by number of creatures.

Wild birds 0.002

Wild land mammals 0.003 (0.02 50,000 years ago – 7x lower now due to human activity)

Marine mammals 0.004 (0.02 estimated 50,000 years ago – 5x lower now due to human activity)

Wild mammals 0.007 (total of above 2 categories)

Humans 0.06

Livestock 0.1

Fish 0.7

Anthropods 1 (small creatures like insects, arachnids and crustaceans)

Fungi 12

Bacteria 70 (mostly deep subsurface)

Plants 450 (of which 10 is human cultivation) – total plants was 2x higher before human civilization

Total 550 Giga tonnes of carbon

Typical uncertainties are in the range of twofold to an order of magnitude.

It's interesting to see that the total weight of humans is estimated at an order of magnitude above wild animals, and that livestock is a corresponding order of magnitude above humans. So livestock, by weight, is over 100 times that of wild animals.

It's also notable that although human presence removes a majority of wild animals it has actually increased the total animal biomass, according to these estimates, because the human and livestock biomass is greater than the wild animal biomass it replaces. That may indicate that a human + livestock system is actually a more efficient way of sustaining life than wild animals. Although I'm not sure if the estimates of 50,000 years ago are likely to be that accurate! And this of course does not account for the poor quality of life of livestock or injustice under the current "efficient" system.

However human presence has reduced the plant and total biomass.

In any case, it's possible to live a more sustainable and lower impact (i.e. more wild animals) lifestyle by doing I would suggest three things. 1: Becoming vegan. 2: Taking care to live in an environmentally friendly way, e.g. zero waste, carbon emission cuts. 3: If you are wealthy by global standards, buy only what you need and a few luxuries. For the rest, invest for the future, retire earlier, and therefore earn and spend less money in your life as a result.

 

[Jamie in Chile]

A related study from a few years ago:

"The number of wild animals on Earth has halved in the past 40 years, according to a new analysis. Creatures across land, rivers and the seas are being decimated as humans kill them for food in unsustainable numbers, while polluting or destroying their habitats, the research by scientists at WWF and the Zoological Society of London found."

That is broadly consistent with the newer report which showed a larger decline extending back over a longer period of time.

If the below graph is true, then reversing wild animal populations declines could be achieved by sevearal things combined including specific protection iniatives such as stopping poachers (presumably coming under "exploitation"), cutting CO2e emissions, and reduced overall consumption (which would presumably have a positive effect on habitat loss and degradation) if less factories need to be built for example to make iphones, then a section of forest might not need to be cleared.

A possible concern is this "less consumption" might be that it might have a negative effect on employment in the developing world.

 

[Skylark]

What amount of biomass is insects?

 

[Jamie in Chile]

Anthropods https://en.wikipedia.org/wiki/Arthropodare 1 out of 550 total, and anthropods contain insects and other things, so insects biomass is less than 1. As far as I can tell, there is no specific estimate for insects. The study comments "insects ...relative biomass fraction is miniscule."

I did find an estimate in the study, citing another study, that 10 to the power 18 is the number of insects in the world (although they extrapoltated from one area of England to the rest of the world, which sounds dubious). If it were accurate, it would mean that there are many millions, perhaps hundreds of millions of insects in the world for each human. Does that sound right? Seems high.

I wonder what has more moral and spiritual worth, or more combined ability to feel emotions and suffer and feel pain and pleasure, hundreds of millions of insects or one human? If the answer is not obvious, then it means that neither is it obvious what has more moral and spiritual worth - all the humans on the planet, or all the insects.

I wonder if biomass could be used as a proxy to estimate the moral value of living creatures in the animal kingdom, since larger animals tend to be more intelligent ones. This only works if you believe, as I do, that sentience and consciousness is on a sliding scale rather than a yes/no thing. Obviously it would be a very imperfect way of thinking about it (it would mean a cow is worth more than a human for instance), but it seems better than going off the number of individuals, or trying to come up with some incredibly complex scheme. The other alternative is just saying it's an impossible question which doesn't seem to be right either.

There may be some kind of moral value in lesser creatures even if they are not sentient or capable of suffering, and are just automatons, on the basis that they can evolve into intelligent creatures later.

 

[Skylark]

Anthropods https://en.wikipedia.org/wiki/Arthropodare 1 out of 550 total, and anthropods contain insects and other things, so insects biomass is less than 1. As far as I can tell, there is no specific estimate for insects. The study comments "insects ...relative biomass fraction is miniscule."

I did find an estimate in the study, citing another study, that 10 to the power 18 is the number of insects in the world (although they extrapoltated from one area of England to the rest of the world, which sounds dubious). If it were accurate, it would mean that there are many millions, perhaps hundreds of millions of insects in the world for each human. Does that sound right? Seems high.

I wonder what has more moral and spiritual worth, or more combined ability to feel emotions and suffer and feel pain and pleasure, hundreds of millions of insects or one human? If the answer is not obvious, then it means that neither is it obvious what has more moral and spiritual worth - all the humans on the planet, or all the insects.

I wonder if biomass could be used as a proxy to estimate the moral value of living creatures in the animal kingdom, since larger animals tend to be more intelligent ones. This only works if you believe, as I do, that sentience and consciousness is on a sliding scale rather than a yes/no thing. Obviously it would be a very imperfect way of thinking about it (it would mean a cow is worth more than a human for instance), but it seems better than going off the number of individuals, or trying to come up with some incredibly complex scheme. The other alternative is just saying it's an impossible question which doesn't seem to be right either.

There may be some kind of moral value in lesser creatures even if they are not sentient or capable of suffering, and are just automatons, on the basis that they can evolve into intelligent creatures later.

Thank you for your thoughtful reply, Jamie. We don’t know each other yet, so I should clarify that my intention was not to trivialize insects. I was more curious as to the impact that humans are having on the realm of bugs. It may be that certain kinds of insects will adapt far better to the type of earth we are creating than we humans may. And others will vanish like so many relatives who are furry, feathered, or finned.