The average peat accumulation rate at a very slow rate between 0.1-0.6 mm/year.
Pea Bullock: 0.12 mm/year (0.1 Mg C/ha/yr) during the past 17,000 years and 0.40 mm/year (0.2 Mg C/ha/yr)   from 17-30k years
Tao Sipinggan: 0.44 mm/year (0.2 Mg C/ha/yr)
Pea Sim Sim & Pea Sijajap: 0.27 mm/year (0.1 Mg C/ha/yr) for the past 10,000 years and 0.69 mm/year (0.4 Mg C/ha/yr) for the past 10-20k year
In summary, these peats are high value carbon stock and stores record of our past 30,000 years. It is the oldest peat in Indonesia, 3 times older than lowland peats in South Sumatra (Fujimoto et al., 2019).

Conclusions

Peatlands in Humbang Hasundutan are unique tropical ecosystem formed primarily from accumulated tree matter, show significant variations in peat layer thickness.  Large areas remain exploited and degraded. The resultant drainage has led to a range of problems, including peat oxidation, subsidence, CO2 emissions, water supply reduction, biodiversity loss, and increased fire hazards. Studies indicated that the abandoned peatlands had lost half of its C stock, while the ones used for agriculture had lost almost 90% of its C content. 
Several extensive areas make up the Toba peatlands. Among them are Dolok Sanggul and Pollung to the west, and Lintongnihuta to the east. The extent of these peatlands remains unconfirmed due to limited studies. A study from 1970s indicated that the bottom of the peat is approximately 30,000 years old.  Additional sites offered crucial data on the age and accumulation rates of peat of 0.1-0.6 mm/year, highlighting the slow formation of these ecological resources.
In conclusion, these highland peatlands are high-value carbon stocks that store records from our past 30,000 years. Notably, they are significantly older than the lowland peats in South Sumatra. The preservation and further study of these peatlands are vital to improving our understanding of historical climate and vegetation changes and their role in the current and future environment.