Cascades Butterfly Project (U.S. National Park Service)

Black and yellow butterfly with red spots perched on a cluster of small pink flowers — Clodius parnassian, a high-altitude butterfly species
NPS / Cathy Clark

MAY 2018
The Cascades Butterfly Project is a long-term monitoring program where citizen scientists (volunteers) and National Park Service Biologists monitor subalpine butterflies and plant phenology.

Butterflies and plants are sensitive indicators of climate change because air temperature influences their life cycles and their geographic distribution. As butterflies develop from egg to larvae to pupae and finally to full maturation, temperature thresholds may trigger these changes. Plant budburst, flowering, and fruiting times are also influenced by temperature and precipitation. Butterflies depend on plants as host plants – providing nectar or shelter for eggs and developing larvae.

Four people with buttefly nets and other survey equipment on a mountain, with more mountains in the distance — Butterfly survey crew on Sauk Mountain
NPS

Climate models project warmer summers, earlier snowmelt, more frequent forest fires, and changes in distributions of plants and animals, but not details on how species in our area will respond to these conditions. Studies in Europe and California have documented range shifts in butterflies in response to changing temperatures. Some species have moved northward or to higher elevations to track their optimal temperature range.

We are monitoring butterflies and plant flowering patterns to understand pollinators to understand how species in our parks are being influenced by warmer climates.

Map of survey sites and the protected areas they occur in. — Map of survey sites

What Are We Doing?

We are monitoring butterfly abundance and plant phenology at ten permanent survey sites in two national parks and two national forests:

North Cascades National Park Service Complex
Mount Rainier National Park
Mount Baker-Snoqualmie National Forest
Okanogan-Wenatchee National Forest

Monitoring Objectives

Monitor long-term trends in butterfly species richness and population abundance in select areas
Monitor long-term trends in plant phenology
Engage citizen scientists in collection of data and communication of information to the general public
Provide field science internship opportunities to young scientists
Provide data to national parks and forests to inform and adapt land management practices as climate changes

Person with a butterfly net walks along a scenic trail — Butterfly survey at Easy Pass in North Cascades National Park.
NPS

Monitoring Methods

Butterfly abundance and plant phenology is monitored along ten 1-kilometer survey routes in two national parks and two national forests
Monitoring is conducted weekly from snow-melt (~early July) until the first frost (~early September)
Butterfly abundances are monitored using the Pollard Walk method
Butterfly data are stored in partnership with the North American Butterfly Monitoring Network’s Pollard Base database (NABA) and Butterflies and Moths of North America

What Have We Found

Each year we have completed more surveys and documented more species with our volunteers and interns.

**Table 1**. Summary of surveys completed by year.
Year	# Surveys	# Species	# Butterflies
2011	29	23	819
2012	29	21	480
2013	34	21	1,585
2014	65	30	2,519
2015	100	36	4,431
2016	82	37	3,573
2017	88	34	3,276

We have also found that peak butterfly abundance changes each year as snowmelt and summer temperatures change. In the graph below you can see the total number of butterflies found each week on surveys of Sauk Mountain in the Mount Baker-Snoqualmie National Forest. Notice the light blue line for 2015 which was a very warm and dry year with early snowmelt. Butterfly numbers peaked July 2-18 – about 3 weeks earlier than most other years. The table lists the dates of peak butterfly abundances on each route for 2015, 2016, and 2017. We are busy analyzing plant flowering times, but they seem to follow a similar pattern (earlier in warm, dry years).

Line graph with butterfly abundance throughout the summer represented by a different line for each year. The greatest, and earliest, peak abundance occurred in 2015. — Butterfly abundance at Sauk Mountain, 2011-2017

**Table 2**. Peak butterfly abundance by route and date for 2015 - 2017.
Site	2017 Date	# Butterflies	2016 Date	# Butterflies	2015 Date	# Butterflies
Cascade Pass	Aug 17	71	Aug 29	116	Aug 11	111
Easy Pass	Jul 25	132	Aug 4	118	Jul 14	169
Maple Pass	Aug 2,9	40	Aug 3	35	Jul 14	24
Sauk Mountain	Aug 7	231	Aug 19	183	Jul 7	361
Skyline	Aug 9	78	Aug 15	67	Jul 7	125
Mazama	Aug 4	45	Aug 25	87	Jul 6	242
Naches	Aug 11	66	Aug 19	59	Jul 8	96
Skyscraper	Jul 25	99	Aug 15	58	Jul 15	99
Sunrise	Aug 1	88	Aug 16	90	Jun 30	113
Spray Park	Jul 31	56	Aug 24	49	Jul 15	72