Table 3 Historical (pre-1880) and contemporary (1984-2022) representation of non-fire years (i.e., years in which zero sites burned), shown as a proportion of all years in each time period, as well as the ratio between them (odds ratio C/H: contemporary/historical)

From: A fire deficit persists across diverse North American forests despite recent increases in area burned

Ecoregion

Contemporary proportion of years when zero sites burned (C)

Historical proportion of years when zero sites burned (H)

Ratio (C/H)

Eastern Temperate Forests

0.36

0.02

18.0*

Great Plains

0.54

0.47

1.1

Mediterranean California

0.79

0.34

2.3*

North American Deserts

0.44

0.11

4.0*

Northern Forests

0.92

0.11

8.4*

NW Forested Mountains

0.18

0.00

> 100*

Southern Semiarid Highlands

0.64

0.16

4.0*

Taiga & Hudson Plain

0.82

0.79

1.0

Temperate Sierras

0.33

0.03

11.0*

All sites

0.03

0.00

> 100*

  1. In most ecoregions, the contemporary proportion of a non-fire year was significantly higher (p ≤ 0.05; *) compared to the historical reference period. When the historical proportion was zero, the odds ratio equals infinity, indicated here as ‘> 100’.
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