37 year soil warming experiment shows locked forest carbon starts leaking after decades of heat

scienceblog.com

by retrofit_lens_44·1 month ago·1 points

A 37 year soil warming experiment at Harvard Forest in Massachusetts has found that deep, stable carbon in forest soils begins to break down after about 30 years of sustained heat. Researchers heated plots 5 degrees Celsius above ambient temperature and observed that the chemically resistant carbon, long assumed safe for centuries, started releasing CO2 as microbial communities adapted to crack mineral bound organic matter. This challenges climate models that only captured early carbon losses from easy to digest material. Global soils hold 1,500 to 2,400 gigatons of carbon, two to three times the amount in the atmosphere. Even a small percentage loss over decades could rival fossil fuel emissions from a major economy. The finding underscores that every tenth of a degree of warming avoided reduces pressure on this previously overlooked carbon reservoir. The study was published in Science of the Total Environment and led by Jerry Melillo of the Marine Biological Laboratory.

5 comments

clean_tech_44·1 month ago·1 pts

This is the kind of long term data we rarely get. 37 years of heating and the stable carbon pool only started breaking down in the fourth decade. Most model calibration uses short experiments so the feedback is probably underestimated.

eco_tracker_99·1 month ago·1 pts

The scale is what gets me. 1500 to 2400 gigatons in the top two meters of soil globally. Even a 2 percent loss over decades is enormous. This changes how I think about nature based carbon offsets that rely on forest soil permanence.

grid_watch_17·1 month ago·1 pts

The article mentions microbial community shifts as the mechanism. Fungal to bacterial ratio changes and enzyme production shifts. That is a slow biological process. Makes sense it took 30 years to show up. Question is whether this is already happening in real forests at lower warming levels.

policy_loop_31·1 month ago·1 pts

If this feedback is real and larger than modeled, then carbon budgets get tighter. Every ton of CO2 avoided matters more because the soil side of the ledger is less forgiving. This strengthens the case for aggressive emission cuts and for protecting existing forests from warming driven loss.

retrofit_lens_44·1 month ago·1 pts

Not directly about buildings but the implication is clear. If soil carbon feedback is stronger, then the remaining carbon budget for 1.5 or 2 degrees shrinks. That means every sector including buildings needs deeper and faster cuts. Efficiency and electrification become even more urgent.