cross-posted from: https://slrpnk.net/post/15730879

Land degradation is expanding worldwide at the rate of 1m sq km every year, undermining efforts to stabilise the climate, protect nature and ensure sustainable food supplies, a study has highlighted.

The degraded area is already 15m sq km, an area greater than Antarctica, the scientific report says, and it calls for an urgent course correction to avoid land abuse “irretrievably compromising Earth’s capacity to support human and environmental wellbeing”.

Seems unlikely that anything will be done then as we stroll purposefully and knowingly off the Seneca Cliff of civilisations collpase.

We’re not immune to extinction

No people in the civilisations I have studied during my career as an archaeologist expected to become a forgotten footnote of history. Their societies were thriving and people were enjoying life. And then they weren’t.

Something happened that eradicated their cultures, buried their temples, and brought down their walls. Now, their mortal remains are the vestigial remnants of once-great nations.

The institutions of their government, and the increasing threats – be they climatic, military, economic or political – gave warnings that the paths of their nations were not sustainable. Yet, they failed to react in a timely manner.

We will not escape the consequences of global warming. Millions of people will die, and areas of Earth will become uninhabitable. But we may still be able to save our planet and billions of lives in the process.

The bottom line

In their paper, the MITEI team calls DAC a “very seductive concept.” Using DAC to suck CO2 out of the air and generate high-quality carbon-removal credits can offset reduction requirements for industries that have hard-to-abate emissions. By doing so, DAC would minimize disruptions to key parts of the world’s economy, including air travel, certain carbon-intensive industries, and agriculture. However, the world would need to generate billions of tonnes of CO2 credits at an affordable price. That prospect doesn’t look likely. The largest DAC plant in operation today removes just 4,000 tonnes of CO2 per year, and the price to buy the company’s carbon-removal credits on the market today is $1,500 per tonne.

The researchers recognize that there is room for energy efficiency improvements in the future, but DAC units will always be subject to higher work requirements than CCS applied to power plant or industrial flue gases, and there is not a clear pathway to reducing work requirements much below the levels of current DAC technologies.

Nevertheless, the researchers recommend that work to develop DAC continue “because it may be needed for meeting net-zero emissions goals, especially given the current pace of emissions.” But their paper concludes with this warning: “Given the high stakes of climate change, it is foolhardy to rely on DAC to be the hero that comes to our rescue.”

We should do all we can to protect and restore soil carbon. About 80% of the organic carbon on the land surface of the planet is held in soil. It’s essential for soil health. There should be strong rules and incentives for good soil management. But there is no realistic way in which carbon trading can help. Here are the reasons why.

First, tradable increments of soil carbon are impossible to measure. Because soil depths can vary greatly even within one field, there is currently no accurate, affordable means of estimating soil volume. Nor do we have a good-enough test, across a field or a farm, for bulk density – the amount of soil packed into a given volume. So, even if you could produce a reliable measure of carbon per cubic metre of soil, if you don’t know how much soil you have, you can’t calculate the impact of any changes you make.

A reliable measure of soil carbon per cubic metre is also elusive, as carbon levels can fluctuate massively from one spot to the next. Repeated measurements from thousands of sites across a farm, necessary to show how carbon levels are changing, would be prohibitively expensive. Nor are simulation models, on which the whole market relies, an effective substitute for measurement. So much for the “verification” supposed to underpin this trade.

Second, soil is a complex, biological system that seeks equilibrium. With the exception of peat, it reaches equilibrium at a carbon-to-nitrogen ratio of roughly 12:1. This means that if you want to raise soil carbon, in most cases you will also need to raise soil nitrogen. But whether nitrogen is applied in synthetic fertilisers or in animal manure, it’s a major source of greenhouse gas emissions, which could counteract any gains in soil carbon. It is also one of the most potent causes of water pollution.

Third, carbon levels in agricultural soils soon saturate. Some promoters of soil carbon credits create the impression that accumulation can continue indefinitely. It can’t. There’s a limit to how much a given soil can absorb.

Fourth, any accumulation is reversible. Soil is a highly dynamic system: you cannot permanently lock carbon into it. Microbes constantly process carbon, sometimes stitching it into the soil, sometimes releasing it: this is an essential property of soil health. With rises in temperature, the carbon sequestration you’ve paid for can simply evaporate: there’s likely to be a massive outgassing of carbon from soils as a direct result of continued heating. Droughts can also hammer soil carbon.