The Anthropocene, the geological epoch where human activity is visible in geologic strata, is often framed with a coming-of-age story: Society must use its new knowledge about earth systems to play an active role in earth stewardship. In some versions, this extends to taking responsibility for designing or managing ecological processes. However, designing or managing ecosystems increasingly involves using emerging technologies for environmental modification that may require specialist expertise or high capital, provoking questions of who has the ability to choose, use, or design these technologies. This dissertation explores four “ecotechnical imaginaries” on varying scales: (1) “negative emissions technologies” such as bioenergy with carbon capture, which are included in climate models; (2) the “blue revolution”, or new forms of ocean-based food and energy production; (3) restoration or management of California’s Salton Sea; and (4) solar geoengineering in the Arctic. The key question addressed in this dissertation is: By what means or processes can citizens have more agency in intentional environment-making? Fifty-five extended interviews were conducted, primarily in Finnish Lapland and California’s Imperial Valley, to explore citizen and stakeholder perceptions of opportunities for public participation in environmental decisions and design. From looking at these four imaginaries together, three major themes emerge. First, public engagement with environmental futures often takes the form of rationally selecting between ready-made options. This “selectability” fits with familiar forms of participation in contemporary life, such as shopping, clicking, and representative democracy. Agency construed as an ability to choose is a very limited form of agency, and actors are generally constrained from shaping environmental technologies themselves. However, civil society actors do work on generating compelling narratives and metrics to improve the selectability of particular futures. Following on work by STS scholars, sociologists, anthropologists and human geographers, who have observed that anticipations of the future are made through practices of quantifying, performing, and imagining, I trace how selectable environmental futures are produced by multiple actors through mutually constitutive combinations of metrics and narrative in these four imaginaries. When citizens are able to shape which options are selectable, there is greater room for other important processes of ecological future-shaping, such as making and taking responsibility. The second key theme involves how the narrative of responsibility in the Anthropocene should be modified to deal with entanglements like burden and agency, and to emphasize response. Selection between futures in a moment of decision cultivates a type of one-off responsibility that curbs agency in the long run. I join other sociologists of the Anthropocene in calling for a continual notion of responsibility, which focuses on responsibility as not a moment of taking the right decision among predetermined options, but as responsibility as a continual process of care and maintenance that recognizes labor and agency. The third major theme is that the imaginaries are serving purposes other than their stated purpose. In this case, rather than deploy climate engineering, restore the Salton Sea, or harness ocean life and energy, the work done by these ecotechnical imaginaries serves other ends besides material transformation: legitimating business as usual or states, performing responsibility without taking it, haunting the climate policy discussion and strengthening the case for other climate pathways, providing jobs for professional calculators, and creating speculative investment in the moment, among others. Social science that looks at imaginaries across scales can help illustrate the work these imaginaries do, which can help citizens shape them towards different ends. The conclusion argues that the selectable and calculable nature of these ecotechnical imaginaries belies the fact that certain disciplines have more privilege in constructing the future, and that an interdisciplinary field of “future studies” grounded in empirical work from fields like sociology, anthropology, and human geography is much needed to better make and take continual responsibility for ecological flourishing.