Peatlands - where and why

• Water table is near the surface
• Peat is 50% carbon
• long-term storage of atmospheric carbon contains up to 1000 Pg C
• 30% of global terrestrial carbon stock - twice that of forests

Distribution

• High-latitude peatlands represent 90% of global peatland area
  • The main factor is effective moisture
• Finland has the most peatlands by area of anywhere inthe world (30% of land area)
• When ppt > evapotranspiration peatlands can occur (temp vs. precipitation ratio)

Peatlands as environmental archives

Environment Archives - Peatlands

• Nowadays, much research in peatlands is about studying their response to climate change and using them for climatic reconstruction

Carbon role

• Their importance has been undervalued in IPCC and other sources
• Nature anc Climate Change 2020 articlesummarizing agents of change impacting global peatland carbon balance
  • Temperature - earming increases plant productivity, but also can enhance decomposition
  • atmospheric pollution - nitrogen deposition
  • sea level change - isostatic uplift allows new peatland formation, but this may be offset by sea level rise
  • Fire - direct peat/carbon loss
  • permafrost melting - increased methane emissions (thermokarst)
  • moisture - habitat changes - peatlands drying (ecohydrological changes)

Past and Ongoing Processes

• Postglacial initiation
• Horizontal expansion

Kaamanen peatland

• Has expanded since its inception and continues to
• Heiskanen et al. 2021. We studied CO2 and CH4 exchange of a subarctic fen and found both sensitivity and inherent resilience in their response to meteorological variation.

Drying landscapes in the arctic

• 60-70% of surface areas of palsa mounds have strongly declined. This is a natural process usually, but under the current climate conditions no new ones are forming
• Permafrost (palsa) collapse forms aapa mires, so we need to understand the C functioning of these ecosystems and how they will continue to change

Carbon Dynamics

Simplified

• In fens (typical arctic peatlands), lots of methane is emitted and some Co2 is absorbed
• In bogs more atmospheric CO2 is absorbed and some methane is emitted
• In permafrost peatlands things are complicated but generally lots of gases are emitted

New C sinks emerging in the arctic

• In Svalbard newly initiated organic soil accumulation seems to be growing. However if it gets much warmer than they will need more precipitation to keep this up.
• Similar pattern in Greenland. Effective moisture conditions in the future are essential for determining if these will stick around
• Arctic peatland expansion with warming - ICAAP project, uses remote sensing to identify these patterns, supplemented by core samples

Possible future scenarios

• Fen-bog transition causing cooling
  • This has happened through history and is occuring currently
  • However if we lose precipitation they would just dry up
  • Biodiversity loss during fen-bog transition? Typically fen vegetation can also live in bogs so there is not a major risk of extinction/extirpation (they are just more abundant in fens)
• Permafrost thaw causing warming (positive feedback)
• Increase in plant productivity/tree line advance causing cooling
  Peatlands - Research applications