Sierra Club Achieves 230% Growth in New Online Donors with Data Axle Nonprofit’s Strategic Digital Segmentation
Sierra Club, the most enduring and influential grassroots environmental organization in the United States, sought to assess the impact of enhanced one-time and sustainer acquisition through additional digital communications.
As a partner of Sierra Club, Data Axle Nonprofit leveraged its data modeling and digital strategy expertise to drive this initiative. The focus was on creating digital audiences that would complement and reinforce direct mail efforts, while testing the effectiveness of digital outreach in driving donor acquisition and revenue. What began as a 3-month test turned into an annual program.
In today’s increasingly digital world, it’s challenging to measure success with top-of-funnel marketing efforts. Are the ads reaching enough people? Are people paying attention to a 30-second CTV spot? What happens to their donation when it’s attributed to another channel? Is it worth the cost? All of these are questions nonprofits and agencies alike are asking themselves when budgeting, testing, measuring results, and considering roll-out.
Top-of-funnel marketing efforts such as CTV, Display, and Meta spread a wide net, but the goal is repetitive brand recognition that will move prospects down the funnel to ultimately contribute to the organization’s purpose.
Sierra Club’s goal was to reach and engage prospects through digital channels while maintaining the momentum of its direct mail efforts. The key objective was to understand how digital marketing could add value and boost donor engagement without dismantling the traditional direct mail approach.
Additionally, the organization wanted to measure the impact of multiple touchpoints—direct mail and digital—on donor behavior and the overall return on investment (ROI). Understanding which audience segments were most responsive to digital outreach and how this impacted new donor and sustainer acquisition, as well as revenue, was critical for future campaign planning.
Layered on top was the goal of acquiring new sustainers.
Data Axle developed a modeled audience for Sierra Club using donor data from our established omnichannel donor cooperative. The digital model integrated Sierra Club’s current digital donors with high-affinity audiences and likely digital donors.
With the additional goal of acquiring new monthly donors, Data Axle incorporated Audience Indicators to identify prospects likely to become sustainers. Audience Indicators take a comprehensive view of data from thousands of nonprofits to identify donors who fall into specific categories, rather than relying on custom modeling that pulls from a limited pool of donors.
The Sustainer Indicator was layered onto the digital model to create a separate audience whose attributes indicated an affinity for becoming a monthly donor. Corresponding direct mail acquisitions were incorporated into the campaigns, timed with approximate in-home dates, to maximize exposure for prospects and lapsed donors.
Throughout the evolution of the project—from December 2024 through June 2025—Data Axle and Sierra Club learned that as the program continued to build, opportunities arose to refine and expand. This applied to audience, creative, media spend, and segmentation.
Not only were audiences meticulously refined throughout the year, but creative walked hand in hand, building an arsenal of creative assets that could be rotated in and out based on front-end (click/engagement) and back-end (donation) behavior.
As the digital model with sustainer indicators rose to the top of front-end performance, the audience was further refined via segmentation, creating three personas:
1. Ready Donors: The highest-quality prospects within the Sustainer model. While this audience is smaller in size, their position toward the bottom of the funnel delivers strong efficiency and revenue impact. These donors connect most with wildlife-focused creative.
2. The Persuadables: The largest and most scalable segment. These donors are actively engaged and moving closer to conversion, making them critical for growth at scale. Persuadables were active with both advocacy and wildlife creatives.
3. Curious Clickers: Often representing a donor’s first online interaction with Sierra Club, these highly engaged clickers and CTV viewers are at the top of the funnel. While they are not immediately conversion-ready, strong engagement with policy and advocacy content helps to fuel long-term donor pipeline by building awareness and trust. These clickers were very active with advocacy and policy creatives.
As the test grew into an annual program, so did results!
Learnings throughout the lifecycle of the annual program led to new strategies and optimizations, resulting in more donation activity.
Efficiency & Revenue Contributions: Every impression delivered measurable value.
1. Ready Donors
2. The Persuadables
3. Curious Clicker
Impact: Together, these segments power a sustainable, full-funnel growth model—efficient today, scalable tomorrow, and built for long-term impact.
This case study demonstrates how strategic digital audience modeling and segmentation can transform donor acquisition programs. The learnings from this annual program have established a framework for continued optimization and growth.
Sierra Club and Data Axle Nonprofit continue to refine their approach, leveraging insights from audience behavior, creative performance, and channel effectiveness to maximize donor acquisition and sustainer growth across all touchpoints.
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