A Plague of People?

Alien Ecologists 

What would alien visitors studying Earth's ecology for the first time conclude? Let's stop thinking about ourselves as something special for a while and instead, think of ourselves as just another species of mammal. Where do we fit in Earth's ecological system?

Where did we fit?

Before we discovered how to make tools, we probably sat somewhere in the lower-mid part of the predator hierarchy. Technology changed that. 

Once we developed clubs, spears and arrows we moved up the predator ladder. Weapons and co-operative hunting techniques enabled us to kill animals much larger and more dangerous than our unarmed selves. It is no coincidence that, wherever we went, the giant mammals that once ruled the land died out. Technology continued to advance to the point where, today, we are the apex predator, all across the globe.

The Agriculture Problem

The beginnings of agriculture seems to be the domestication of pigs in Mesopotamia around 11,000BC. Prior to that, humans were hunter-gatherers and as such would have had relatively little impact on the landscape. They lived in and with their natural environment.

As agriculture extended to other crops and livestock, and the population grew, farming spread across the land. Today, 50% of the habitable land on the planet is occupied by it. That is 50% of the habitable land denied to the natural species that went before. 50% of the available land where the original plant and animal occupants are excluded and usually exterminated as pests.

The Population Problem

As I write this, the Earth's population is estimated at a little above 7.7 billion people and increasing. By the end of this century, the UN predicts it will be just under 11 billion. As compared to other mid-sized mammals, this is a huge number. For example, estimations for other common widely distributed species range in the low-mid tens of millions for dolphins up to about a billion and a half for domestic cattle (and they are only there because of us). As for one of our closer animal relations, the chimpanzee, there are only somewhere between 172,000 and 300,000 left.

The effects of us

In what is a geological instant, Earth has gone from being a place of abundance to one of all manner of threats to its many species of flora and fauna. To name a few, these include:

• Being hunted/harvested to extinction.
• Desertification
• Loss of habitat or food sources due to competition from humans.
• Pollution.
• Conversion of natural habitats for other purposes by humans.
• Deliberate poisoning by humans to prevent competition for food sources (i.e. crops).

And I haven't even mentioned the biggie; climate change, which is significantly contributed to by that one species; us. Sorry, but the ever-growing body of science on that subject is now pretty much conclusive.

The Alien Solution

Our alien visitors would see the great numbers of humans compared to the populations of other species. They would also see the vast areas of Earth damaged by agriculture. 

From their observations, our alien visitors would likely conclude Earth's ecosystem is way out of balance. I think they would go so far as to conclude that humans were present in plague proportions.
Given humans' propensity for driving other species to extinction, devouring Earth's resources as if there was an infinite supply (there isn't) and generating all sorts of harm to the planet's biosphere, our alien visitors could justifiably conclude we were a pest species.
Would our alien visitors then conclude that they would be doing Earth a service by exterminating us, so that the millions of other species of life on Earth could survive?

Looking at Earth from the perspective of all its life forms, what have we done to make it a better place?

Will more CO2 in the air make plants grow faster and give us more food?

Recently, one of my acquaintances, in a discussion about climate change, put forward the argument that more carbon dioxide (CO2) in the atmosphere might be a good thing, because it encouraged plant growth and hence should result in more food being available. I didn't have a ready answer, so I asked Bing AI for help. The following is the (heavily edited and reference-checked) result.

Most educated people now accept that CO2 is a gas that makes the Earth warmer. This is because CO2 traps heat from the sun and keeps it from escaping back into space; a condition called the greenhouse effect. Humans have been adding CO2 to the air by burning coal, oil, and gas for energy since the beginning of the industrial age in the early 19th century. This was carbon dioxide that has been sequestered deep in the Earth over a period of hundreds of millions of years, gradually bringing the atmosphere to what it was like a couple of centuries ago. Since then, we have returned massive amounts of this CO2 back to the atmosphere all at once, geologically speaking, with the results we are beginning to see right now. This dumping of CO2 back into the atmosphere has caused the Earth's temperature to rise by about 1 degree Celsius since the 1800s. This doesn't sound like much, but it has a big impact on the weather, the oceans, the ice, and the living things on our planet.

However, CO2 is not only a gas that makes the Earth warmer. It's also a gas that plants need to grow. Plants use CO2, water, and sunlight to make their own food in a process called photosynthesis. When plants do photosynthesis, they also make oxygen that we breathe. So more CO2 in the air means more food for plants, right? And more food for plants means more food for us, right?

Well, not so fast. The answer is not that simple. Some scientists have done experiments to see how plants react to more CO2 in the air. They have found that some plants do grow faster and bigger with more CO2, but some plants do not. It depends on what kind of plant it is, and where it grows. For example, wheat, rice, and beans like more CO2, but corn and sugarcane do not. Also, some plants can get more nitrogen from the air than others, which helps them grow better with more CO2, but some plants cannot.

More CO2 in the air does not mean only more food for plants. It also means other changes in the environment that affect plant growth. For example, more CO2 in the air means higher air and ocean temperatures, which upset normal weather patterns. This results in abnormal droughts, flooding and winds in different places. In turn, this results in less, or excessive, water in the soil, changes to soil chemistry, more bugs or diseases that damage plants, and more pollution that harms plant cells. These changes can make plant growth worse or better. It depends on how much conditions change and how these changes interact with each other.

So what does this mean for our food supply? Some scientists have used computer modelling to try to predict how much food we will have in the future with more CO2 in the air. They have used different models that use different data and assumptions. They have also used different scenarios that imagine different human responses and behaviours as conditions change. Unsurprisingly, different results have been found depending on what model and scenario is used. Some models say we will have more food in some places, but less in others. Some say we will have less food everywhere while others say we will have enough food for everyone if we share it well (not a likely proposition if history is any indication).

So what can we do about it? The answer is not easy either. But one thing we can do is to reduce our CO2 emissions by minimising fossil fuel use and utilising more renewable energy sources like solar or wind power. This can help slow down global warming and climate change and give us more time to adapt to them. We can also protect and restore our land ecosystems like forests, grasslands, and wetlands that store carbon and help regulate the climate. This can help reduce CO2 in the air and provide other benefits like clean water and greater biodiversity. And we can improve our farming practices by using less water and fertiliser, and by adopting more regenerative methods. We may also need to change what we produce, and where, to adapt to changes to conditions and make more efficient and environment-friendly use of the land. This may in turn require us to change our diets to match what the Earth is still capable of producing.

My own opinion, supported by the evidence of recent exceptional droughts, floods, hurricanes and similar climatic events in a number of the world's food-producing areas is that more CO2 in the atmosphere will result in continued warming and further devastation of food crops, resulting in a significant decline in food production.

References

Kimball BA (1983) Carbon dioxide and agricultural yield: an assemblage and analysis of 430 prior observations. Agron J. 75:779–788

Ainsworth EA and Long SP (2005) What have we learned from 15 years of free-air CO₂ enrichment (FACE)? A meta-analytic review of the responses of photosynthesis transpiration and yield to rising CO₂.

New Phytol. 165:351–372

Hättenschwiler S et al (2011) Atmospheric CO₂ enrichment of terrestrial ecosystems – retrospect

and prospect. Crit Rev Plant Sci. 30:1–40

Parry ML et al (2004) Effects of climate change on global food production under SRES emissions

and socio-economic scenarios. Glob Environ Change. 14:53–67

Müller C et al (2014) Implications of climate mitigation for future agricultural production.

Environ Res Lett. 9:124018

Valin H et al (2014) The future of food demand: understanding differences

in global economic models. Agric Econ. 45:51–67

Myers SS et al (2014) Increasing CO₂ threatens human nutrition.

Nature. 510:139–142

Smith P et al (2013) How much land-based greenhouse gas mitigation can be achieved without compromising food security and environmental goals?

Source: Conversation with Bing, 18/05/2023

(1) NASA at Your Table: Climate Change Impacts on Crop Growth. https://www.nasa.gov/feature/goddard/esnt/2021/nasa-at-your-table-climate-change-and-its-environmental-impacts-on-crop-growth/.

(2) Study: Global plant growth surging alongside carbon dioxide. https://www.noaa.gov/news/study-global-plant-growth-surging-alongside-carbon-dioxide.

Do volcanoes contribute to a heating climate?

Why I'm asking 

Over on Twitter, someone complained that I shouldn't be moaning about farmers contributing to climate change. I should be worrying about increased volcanism, because this was a much bigger problem for global warming. So I thought I'd check my facts.

I put the question to my Microsoft friend, Bing and it pointed me to the US Geological Service, which had this to say.

In a Nutshell

The USGS provided some interesting facts:

• Volcanoes do have an influence on climate change.
• Ash from volcanoes has little impact on climate change because they stay in the atmosphere for a short time; days to weeks.
• Volcanic gasses such as sulphur dioxide can cause global cooling.
• Volcanic carbon dioxide can potentially contribute to global warming.

So, we can discount ash as a problem for climate either way, but what about sulphur dioxide and carbon dioxide?

Sulphur Dioxide

Sulphur dioxide has the biggest impact on climate because it is quickly converted to sulphuric acid, which then condenses into sulphate aerosols in the stratosphere. These fine particles are reflective, resulting in more of the Sun's heat being reflected back into space and resulting in cooling of the atmosphere beneath.

In 1991 Mount Pinatubo in the Phillipines erupted, putting out the biggest sulphur dioxide cloud in living memory. This lowered the global temperature for three years, by up to about half a degree Celsius.

Carbon Dioxide

Volcanoes can indeed emit significant amounts of carbon dioxide. Mount St Helens in the USA emitted about 10,000,000 tonnes of carbon dioxide in 9 hours when it erupted in 1980. This seems like a lot, but it takes mankind only 2.5 hours to do the same. 

While large scale eruptions are noteworthy, they are intermittent, whereas our carbon dioxide emissions go on continuously. Scientists estimated that, in one year, mankind would cause carbon dioxide emissions 80 to 270 times greater than all the Earth's volcanoes combined.

Conclusion

I think you know where this is heading.

• Throughout history, mankind has only observed widespread cooling as a result of vulcanism.
• The mechanism for this is sulphate aerosols in the stratosphere reflecting the Sun's heat back into space.
• Volcanic carbon dioxide is a greenhouse gas, but its effect is overridden by the stronger effects of the sulphur dioxide.
• The amount of carbon dioxide emitted by volcanoes is very small compared to that emitted by human activities.

So no, volcanoes do not contribute significantly to a heating climate. Current evidence suggests the reverse. Volcanism generally results in a short term cooling effect.

Other reading:

Eos, Vol. 92, No. 24, 14 June 2011 - Volcanic Versus Anthropogenic Carbon Dioxide