Potential carbon loss associated with post-settlement wetland conversion in southern Ontario, Canada

Table 1 Wetland conversion summary from map overlay analysis

	Tree swamp	Shrub swamp	Fen	Bog	Marsh	Total
Pre-settlement extent (km²)	10,111.68	2191.73	54.75	108.90	12,517.24	24,984.30
Current (2011 CE) extent (km²)	8341.62	1167.46	53.07	88.92	1380.57	11,031.64
Converted extent (km²)	1770.06	1024.27	1.68	19.98	11,136.67	13,952.66
% of Pre-settlement
Remaining (2011 CE)	82.5%	53.3%	96.9%	81.7%	11.1%	44.2%
Converted since 1800 CE	17.5%	46.7%	3.1%	18.3%	88.9%	55.8%
% of converted pre-settlement
Cultivated (tilled^a, tree planting)	50.8%	50.4%	29.2%	42.9%	58.6%	57.0%
Developed (building, road, extraction)	8.7%	9.5%	4.4%	5.3%	6.9%	7.3%
Natural^b (total)	12.4%	11.6%	45.2%	5.0%	9.7%	10.2%
(Rocky—beach, cliff, alvar)^c	(0.17%)	(0.17%)	–	–	(0.80%)	(0.65%)
(Grassland—prairie, tallgrass)	(0.04%)	(0.83%)	–	–	(0.34%)	(0.34%)
(Forest—conifer, mixed, deciduous)	(92.9%)	(85.9%)	(95.7%)	(85.3%)	(80.6%)	(83.0%)
(Open water—deep, unvegetated)	(6.9%)	(13.1%)	(4.3%)	(14.7%)	(18.2%)	(16.0%)
Undifferentiated^d	28.1%	28.6%	21.1%	46.7%	24.8%	25.5%

^a Managed agricultural fields for annual crops (i.e., ‘tilled’) account for > 95% of the cultivated pre-settlement wetlands; tree plantation is relatively sparse
^b This category can include possible errors from the current wetland mapping or an actual ecosystem change resulting from the lowering of water tables in response to drainage in the surrounding area (see main text)
^c This class was exempted from peat carbon stock calculations in Table 4 (see Additional file 1: Appendix S1 for more details)
^d Areas were unidentifiable as specific land classes and may include pastures, orchards, vineyards, abandoned farmlands, urban brownfields, the edge of transportation corridors, upland thicket, and unclassified wetlands [27]

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