# How many monarchs are left

Two long-running counts of two monarch populations, measured in different units by different methods.

## Eastern population: hectares of occupied forest in Mexico

Surveyed each December by WWF Mexico, CONANP and the Monarch Fund annual overwintering survey. Area of oyamel fir occupied by overwintering clusters, surveyed each December.

| Winter | Hectares occupied |
| --- | --- |
| 1993-94 | 6.23 |
| 1994-95 | 7.81 |
| 1995-96 | 12.61 |
| 1996-97 | 18.19 |
| 1997-98 | 5.77 |
| 1998-99 | 5.56 |
| 1999-00 | 9.05 |
| 2000-01 | 2.83 |
| 2001-02 | 9.35 |
| 2002-03 | 7.54 |
| 2003-04 | 11.12 |
| 2004-05 | 2.19 |
| 2005-06 | 5.91 |
| 2006-07 | 6.87 |
| 2007-08 | 4.61 |
| 2008-09 | 5.06 |
| 2009-10 | 1.92 |
| 2010-11 | 4.02 |
| 2011-12 | 2.89 |
| 2012-13 | 1.19 |
| 2013-14 | 0.67 |
| 2014-15 | 1.13 |
| 2015-16 | 4.01 |
| 2016-17 | 2.91 |
| 2017-18 | 2.48 |
| 2018-19 | 6.05 |
| 2019-20 | 2.83 |
| 2020-21 | 2.10 |
| 2021-22 | 2.84 |
| 2022-23 | 2.21 |
| 2023-24 | 0.90 |
| 2024-25 | 1.79 |

Peak 18.19 ha in 1996. Low 0.67 ha in 2013. Most recent 1.79 ha in 2024.

## Western population: Thanksgiving count in California

Counted by the Xerces Society Western Monarch Count. Volunteer counts at California overwintering groves over roughly three weeks around Thanksgiving.

| Year | Butterflies counted |
| --- | --- |
| 1997 | 1235490 |
| 1998 | 564349 |
| 1999 | 267574 |
| 2000 | 394781 |
| 2001 | 209570 |
| 2002 | 99353 |
| 2003 | 209820 |
| 2004 | 205085 |
| 2005 | 221058 |
| 2006 | 86437 |
| 2007 | 86932 |
| 2008 | 130317 |
| 2009 | 58468 |
| 2010 | 143204 |
| 2011 | 92798 |
| 2012 | 144812 |
| 2013 | 211275 |
| 2014 | 234731 |
| 2015 | 292888 |
| 2016 | 298464 |
| 2017 | 192668 |
| 2018 | 27721 |
| 2019 | 29418 |
| 2020 | 1914 |
| 2021 | 247237 |
| 2022 | 335479 |
| 2023 | 233394 |
| 2024 | 9119 |

Peak 1235490 in 1997. Low 1914 in 2020. Most recent 9119 in 2024.

## Caveats

Both are indices rather than censuses. They measure the overwintering generation only, cannot be added together, are extremely noisy year to year, and do not identify a cause.

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Source: https://milkweedusa.com/monarch-population/ — Milkweed USA, CC BY 4.0. Underlying counts are the work of WWF Mexico and the Xerces Society.