Natural wetlands can mitigate ongoing increases in atmospheric carbon by storing any net balance of organic carbon (peat) between plant production (carbon uptake) and microbial decomposition (carbon release). Efforts are ongoing to quantify peat carbon stored in global wetlands, with considerable focus given to boreal/subarctic peatlands and tropical peat swamps. Many wetlands in temperate latitudes have been transformed to anthropogenic landscapes, making it difficult to investigate their natural/historic carbon balance. The remaining temperate swamps and marshes are often treated as mineral soil wetlands and assumed to not accumulate peat. Southern Ontario in the Laurentian Great Lakes drainage basin was formerly a wetland-rich region that has undergone significant land use change since European settlement. This study uses southern Ontario as a case study to assess the degree to which temperate regions could have stored substantial carbon if it had not been for widespread anthropogenic land cover change. Here, we reconstruct the full extent and distribution of natural wetlands using two wetland maps, one for pre-settlement conditions (prior to 1850 CE) and the other for modern-day patterns of land use (2011 CE). We found that the pre-settlement wetland cover decreased by about 56% with the loss most significant for marshes as only 11% of predicted pre-settlement marshland area remains today. We estimate that pre-settlement wetlands held up to ~ 3.3 Pg of carbon relative to ~ 1.3 Pg for present-day (total across all wetland classes). By not considering the recent carbon loss of temperate wetlands, we may be underestimating the wetland carbon sink in the pre-industrial carbon cycle. Future work is needed to better track the conversion of natural wetlands globally and the associated carbon stock change.

中文翻译：

---

与加拿大安大略省南部沉降后湿地转化相关的潜在碳损失。

天然湿地可以通过存储植物生产（碳吸收）和微生物分解（碳释放）之间的有机碳（豌豆）净平衡来缓解大气中碳的持续增加。正在努力量化存储在全球湿地中的泥炭碳，其中相当多的重点放在寒带/南亚泥炭地和热带泥炭沼泽上。温带纬度地区的许多湿地已转变为人为景观，因此难以调查其自然/历史碳平衡。其余的温带沼泽和湿地通常被视为矿物土壤湿地，并假定不会积聚泥炭。劳伦式大湖流域的安大略省南部曾经是一个湿地丰富的地区，自欧洲定居以来，土地使用发生了重大变化。这项研究以安大略南部地区为例，评估了温带地区如果没有大规模的人为土地覆盖变化，则可以储存大量碳的程度。在这里，我们使用两个湿地图来重建自然湿地的完整范围和分布，一个用于定居前的条件（1850年之前），另一个用于现代土地利用模式（2011年）。我们发现，结算前湿地的覆盖率下降了约56％，其中沼泽地的损失最为显着，因为今天仅保留了预计结算前湿地的11％。我们估计，结算前的湿地所含碳量约为3.3 Pg（相对于目前的1.3 Pg）（所有湿地类别的总量）。不考虑最近温带湿地的碳损失，我们可能低估了工业化前碳循环中的湿地碳汇。需要开展进一步工作，以更好地跟踪全球自然湿地的转化以及相关的碳储量变化。