Cascades Butterfly Project

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


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.


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.


# Surveys

# Species

# Butterflies





























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
One person holds a butterfly in a viewing container while another checks a field guide book
Identifying a butterfly in Mount Ranier National Park


For More Information

Learn about volunteering for the Cascades Butterfly Project

Protocols & Procedures

Rochefort RM and McLaughlin JF. 2017. The Cascades butterfly project: A protocol for monitoring subalpine butterflies and plant phenology in the Cascade Mountains of Washington. Natural Resource Report. NPS/NOCA/NRR—2017/1440. National Park Service. Fort Collins, Colorado

Rochefort RM. 2017. The Cascades Butterfly Project: Survey routes, standard operating procedures, and field forms. North Cascades National Park Service Complex. Sedro-Woolley, Washington

In The News

Bush, Evan. "Citizen scientists track effects of climate change in the Northwest." The Seattle Times 7 August 2017.

Mount Rainier National Park, North Cascades National Park

Last updated: July 13, 2023