This study reports on our steps toward achieving a conceptually coherent and empirically validated learning progression for carbon cycling in socio-ecological systems. It describes an iterative process of designing and analyzing assessment and interview data from students in upper elementary through high school. The product of our development process—the learning progression itself—is a story about how learners from upper elementary grades through high school develop understanding in an important and complex domain: biogeochemical processes that transform carbon in socio-ecological systems at multiple scales. These processes: (a) generate organic carbon (photosynthesis), (b) transform organic carbon (biosynthesis, digestion, food webs, carbon sequestration), and (c) oxidize organic carbon (cellular respiration, combustion). The primary cause of global climate change is the current worldwide imbalance among these processes. We identified Levels of Achievement, which described patterns in the way students made progress toward more sophisticated reasoning about these processes. Younger learners perceived a world where events occurred at a macroscopic scale and carbon sources, such as foods and fuels, were treated as enablers of life processes and combustion rather than sources of matter transformed by those processes. Students at the transitional levels—levels 2 and 3—traced matter in terms of materials changed by hidden mechanisms (level 2) or changed by chemical processes (level 3). More advanced students (level 4) used chemical models to trace matter through hierarchically organized systems that connected organisms and inanimate matter. Although level 4 reasoning is consistent with current national standards, few high school students reasoned this way consistently. We discuss further plans for conceptual and empirical validation of the learning progression.
Developing a Multi-year Learning Progression for Carbon Cycling in Socio-Ecological Systems
Learning Progressions for Environmental Science Literacy
We report in this article on learning progression research focusing on how schools can prepare students to be environmental science literate—that is, students and adults should have the capacity to understand and participate in evidence-based discussions about complex socio-ecological systems.1More specifically, we describe our progress in developing a learning progression that focuses on an important and complex domain of knowledge and practice—learners’ accounts of processes that generate, transform, and oxidize organic carbon. We report on students’ reasoning in this domain from upper elementary to high school.
Learning progressions are “descriptions of the successively more sophisticated ways of thinking about a topic that can follow one another as children learn about and investigate a topic over a broad span of time (e.g., six to eight years)” (Duschl, Schweingruber, & Shouse, 2007). They are anchored on one end by what we know about student reasoning about specific concepts entering school (i.e., Lower Anchor). On the other end, learning progressions are anchored by societal expectations (e.g., science standards) about what we want high school and college students to understand about science when they graduate (i.e., Upper Anchor). We conceive of our Upper Anchor—environmental science literacy—as discourse, as practice, and as specific knowledge.
Our broadest definition of environmental science literacy follows Gee’s definition of literacy: “Literacy is control of secondary uses of language (i.e., uses of language in secondary discourses)” (Gee, 1991, p. 8). Gee defines a discourse as “a socially accepted association among ways of using language, of thinking, and of acting that can be used to identify oneself as a member of a socially meaningful group” (Gee, 1991, p. 3), and he distinguishes between primary discourses that we acquire in our homes and secondary discourses that we learn in other social settings.
Following Gee’s definition we see environmental science literacy in part as an “association among ways of using language, of thinking, and of acting” that is apparent in policy debates and media reports about climate change and other environmental issues. For example, the 2007 Nobel Peace Prize was awarded to Al Gore and the Intergovernmental Panel on Climate Change (IPCC) for developing reports and presentations intended to promote public understanding of scientific research on global climate change (Gore, 2006; IPCC, 2007). We discuss below our evidence that for many students these reports are incomprehensible products of an unfamiliar secondary discourse. One goal of our carbon cycle learning progression is to investigate how students make progress toward control of the secondary discourse that produces reports like these.
Environmental Science Literacy as Practice
Like all forms of literacy, environmental science literacy is embedded in verbal and nonverbal practices. Responding to environmental challenges like climate change will require collective human action on an unprecedented scale. This leads to a core question that is the basis for our research: How well prepared are our citizens to understand and respond to research on global climate change? In particular, how will people respond to scientific evidence in their actions in a variety of citizenship roles, such as consumers, learners, voters, workers, and advocates?
In keeping with our definition of environmental science literacy as mastery of a secondary discourse, we focus specifically on the scientific practices that citizens will need to play these roles. Our framework includes three key practices(each of which is actually a complex domain of practice) that are essential for responsible citizenship and that students can engage in as learners: inquiry, accounts, and decision-making in citizenship roles.
While environmental decision-making is the domain of practice that ultimately justifies our research program (see Anderson, 2008; Tsurusaki, Tan, Covitt, & Anderson, 2008), we focus in this article on accounts (explanations and predictions)as a simpler domain of practice that is central to environmental science literacy. Responsible environmental decisions are based on deliberations in which citizens use their knowledge to construct accounts that explain the situation and predict likely outcomes of different courses of action. The practice that is the focus of the carbon cycling learning progression reported here is developing and using accounts of carbon cycling to explain and predict different situations and events.
Environmental Science Literacy as Specific Knowledge
We focus on students’ accounts of carbon transforming processes in part because those accounts reveal the knowledge students have available as a resource for their practices as citizens. The global climate is changing and with this change comes increasing awareness of how the actions of human populations are altering processes that occur in natural ecosystems. The “carbon cycle” is no longer a cycle, on either local or global scales; most socio-ecological systems—especially terrestrial systems2 altered by humans—are net producers or net consumers of organic carbon. Humans have altered the global system so that there is now a net flow of carbon from forests and fossil fuels to atmospheric carbon dioxide. These changes are caused by the individual and collective actions of humans. In a democratic society like the United States, human actions will change only through the consent and active participation of our citizens, which places a special burden on science educators. Responsible environmental decision-making requires citizens to reason about complex systems. In the case of carbon cycling, this reasoning involves accounting for matter transformations that change carbon between organic forms and greenhouse gases, especially carbon dioxide.
Figure 1: Loop diagram for carbon cycling in socio-ecological systems
Human Impact:Waste from human energy use (CO2)
Human Social and Economic Systems Human Actions in