Disparities remain in the representation of marginalized students in STEM. Classroom-based experiential learning opportunities can increase student confidence and academic success; however, the effectiveness of extending learning to outdoor settings is unknown. Our objectives were to examine 1) demographic gaps in ecology and evolutionary biology (EEB) major completion, college graduation, and GPAs for students who did and did not enroll in field courses, 2) whether under-represented demographic groups were less likely to enroll in field courses, and 3) whether under-represented demographic groups were more likely to feel increased competency in science-related tasks (hereafter, self-efficacy) after participating in field courses. We compared the relationships among academic success measures and demographic data (race/ethnicity, socioeconomic status, first-generation, and gender) for UC Santa Cruz undergraduate students admitted between 2008 and 2019 who participated in field courses (N=941 students) and who did not (N=28,215 students). Additionally, we administered longitudinal surveys to evaluate self-efficacy gains during field-based versus classroom-based courses (N=570 students). We found no differences in the proportion of students matriculating at the university as undecided, proposed EEB, or proposed other majors across demographic groups. However, five years later, under-represented students were significantly less likely to graduate with EEB degrees, indicating retention rather than recruitment drives disparities in representation. This retention gap is partly due to a lower rate of college completion and partly through attrition to other majors. Although under-represented students were less likely to enroll in field courses, field courses were associated with higher self-efficacy gains, higher college graduation rates, higher EEB major retention, and higher GPAs at graduation. All demographic groups experienced significant increases in self-efficacy during field-based but not lecture-based courses. Together, our findings suggest that increasing the number of field courses and actively facilitating access to students from under-represented groups can be a powerful tool for increasing STEM diversity.

To evaluate self-efficacy gains during field courses, we administered longitudinal surveys in a subset of three courses between Fall 2016 and Spring 2019: (a) BIOE 20C, a gateway ecology and evolutionary biology lecture course (N=81); (b) BIOE 82, a 2-unit, lower-division field course that is intended to provide early field immersion and introduce natural history information and field research opportunities to students (N=194), and (c) CEC, an immersive 19-unit upper division field course that engages students in student-directed research projects (N=295). While BIOE 20C and BIOE 82 are courses offered at UCSC, CEC is a UC system-wide course that enrolls students from all UC campuses. We administered paired pre- (first week of the academic quarter) and post- (last week of the academic quarter) surveys. Each student was asked to rate their confidence on a 5-point Likert scale (1=Strongly Disagree, 2=Disagree, 3=Neither Agree Nor Disagree, 4=Agree, 5=Strongly Agree) for each of six questions: i) I am familiar with the flora, fauna, and ecosystems of California; ii) I have strong experimental design skills; iii) I have strong oral presentation skills; iv) I know how to conduct field research projects from start to finish; v) I am interested in pursuing a career in science; vi) I am interested in pursuing a graduate degree.

To quantify how the demographics of field courses have changed over time, we extracted historical demographic composition data from field courses taught between 2008 and 2019 (N=1,239 students; courses BIO75, BIO82, BIO128L, BIO151, BIO159, BIO161), and the gateway lecture course for EEB majors (N=11,589 students; BIO20C). Field courses were included if more than 50% of course hours were spent in the field rather than in the classroom and if the course had been taught for at least 4 years.