Public participation in science, or citizen science, is finding a foothold in all branches of science, from ecology to climatology to astronomy. Citizen science can be informal and isolated, as in the amateur astronomer who identified the first asteroid of 2014 (and only the second incoming object ever to be identified before it hit Earth), or part of an organized event with a specific goal in mind such as the National Parks’ “BioBlitzes” to record all the species in a particular Park unit, or even regular ongoing programs of monitoring and discovery, such as the LiMPETS program which works with students and volunteers to monitor coastal animal populations in National Marine Sanctuaries. Citizen scientists are now making significant contributions to our understanding of climate change, emerging infectious diseases, and potentially hazardous near-Earth objects.The number and diversity of projects that have emerged over the last decade is astounding, but they are all rooted in, and reflective of, larger trends occurring across science over this same time period. While my perspective on these trends is from the field of ecology, I believe readers of this journal will find echoes of these trends within their own fields. Specifically, three emerging trends: 1) the renewed power of, and respect for, discovery-driven observational studies; 2) the increasing openness to, and acceptance of, non-institutional knowledge holders; and 3) the rise of crowdsourcing, are aligned to make citizen science a powerful source of scientific insight. And while citizen science isn’t new (it was, in fact, the way that science started long before it became institutionalized), the power of information technology to help us collect, connect, analyze and provide feedback upon large collections of citizen science data is the catalyst allowing for unprecedented uses of citizen science data.The trends in science I refer to above, although facilitated by recent advances in technology, are borne out of very old, even ancient, practices. In particular, the renewed power of observation is rooted in the practice of natural history, which probably co-evolved with us as an essential function of the human species. Natural history is the interdisciplinary study, classification, and interpretation of the living Earth and its inhabitants [1]. Natural history can be separated from merely strolling in the woods, or obsessively pinning butterflies to shadow boxes by its reliance on carefully engaged, multi-sensory observation — what the paleobiologist Geerat Vermeij (who happens to be blind) describes as “the increasingly ignored role of sensation — of observation with the brain in gear”.Yet natural history has long been thought of as wholly within the domain of amateurs, even hobbyists. The amateur tinge of natural history has tainted it and its practitioners for much of the history of modern, professional, and institutionalized science. Charles Darwin was told by his father, “you care for nothing but shooting, rat-catching, and dogs, and you will be a disgrace to yourself and all your family.” Consider the fate of one of America’s greatest natural historians, Teddy Roosevelt. He entered Harvard as an eager young naturalist, hoping to be trained by the great biologists there to become a professional naturalist, but he soon became discouraged, noting the tendency to “treat as not serious, as unscientific, any kind of work that was not carried on with laborious minuteness in the laboratory.” The disdain for natural history became particularly acute in the decades following the discovery of the structure of DNA. Watson and Crick’s discovery provided the tantalizing promise that biology could finally become as orderly and predictable as biologists always assumed physics and chemistry were — so much for the fanciful musings of natural historians. The great naturalist E.O. Wilson, who started at Harvard at the same time as young James Watson, was largely forgotten in the shadows of his colleague’s more brilliant prospects for scientific immortality.This period of late 20th century science was marked by an increasing interest in controlled, hypothesis-driven science. Buoyed by Karl Popper’s philosophical conjecture that science could be reliably separated from non-science by the degree to which a question was falsifiable, a standardized acceptable method of achieving scientific inference emerged. The “scientific method” that most of us were taught in grade school is a reflection of this, as is the fairly standard format for journal papers and grant applications.But late 20th and early 21st century realities of our natural world have shone light on some of the limitations of this conception of scientific methodology, and science as an institution is adapting (in some fields faster than others) to this new reality. Specifically, large scale changes in the environment present complex realities that are impossible — logistically or sometimes ethically — to replicate in laboratories or controlled experiments. At the same time, advances in technology that allow us to observe the natural world at both its largest and smallest scales with unprecedented acuity are making observations of the world — the basic building blocks of natural history — more useful and powerful than they have ever been before. Why try to make an incomplete simulation of a natural phenomenon in the laboratory or on a computer when you can observe the same phenomenon as it occurs in real time and real space? Why limit our investigations to those that can falsify a limited set of pre-determined binary hypotheses, when we can discover unexpected and explanatory patterns across the full spectrum of reality by observing as broadly as possible?These are large and debatable philosophical questions, but just in being able to seriously ask them has a trickle down effect on what we perceive to be “scientific” and, by extension, who we perceive to be scientists. Accordingly, we have seen a slowly emerging respect for both natural history and for amateur observers of the natural world. In part, the practical limitations of what credentialed scientists are able to observe forces our hands to look beyond the ivory tower for knowledge, but the quality, breadth, and utility of this amateur knowledge is what keeps us coming back.The third trend, the rise of crowdsourcing, is also technologically facilitated, but is a novel and emergent effect of the first two. Crowdsourcing is essentially a societal hack for mimicking a powerful biological adaptation for observing change [2]. Namely, biological systems rely on decentralized observational agents to sense and respond to change. The exemplar of this organization is our immune system. It features millions of cells running around our body identifying and attacking pathogens, with virtually no control from our brain. The system and its agents still serve our brain and our body, and are likewise given a home and nutrition, but they act independently. It is their collective action, then, that solves the challenge of how to keep a body protected from dangerous foreign invaders.As a societal parallel of this adaptive process, crowdsourcing has helped to solve all sorts of complex challenges — from long-standing mathematical puzzles to thorny problems in protein configuration — and there are more than a few personal computers still employed in the search for extraterrestrial life in their down time. More primitive, yet effective forms of crowdsourcing can be found at any horse track. Pari-mutuel betting essentially assigns probabilities to the wisdom of crowds. Today’s crowdsourcing is a technological mutation of this more primitive form, allowing for much more widespread, instantaneous, and multi-directional sharing of decentralized observation.Citizen science, in its best manifestations, brings together all these trends and beneficial mutations in science, into a positive feedback cycle. As we increasingly respect the power of observation to understand a complex world, we increasingly seek out observations and observers. In recruiting new observers — as either lone natural historians or participants in formalized citizen science programs — we both educate ourselves as scientists about the skills of amateurs, and provide science education for new observers. And as these observers increasingly come into meaningful and mutually beneficial contact with institutional scientists, the number, quality, and utility of citizen science observations will likely improve.For those scientists interested in delving into the world of citizen science, there is a large and growing literature codifying and analyzing best practices. Additional reading is recommended below which considers citizen science from several angles, most fully generalizable to many fields of professional science.References and additional reading:[1][2] Sagarin, R. 2012. Learning from the Octopus: How Secrets from Nature That Can Help Us Fight Terrorist Attacks, Natural Disasters and Disease. Basic BooksSagarin, R and A. Pauchard. 2012. Observation and Ecology: Broadening the Scope of Science to Understand a Complex World. Island PressEcological Society of America. 2012. Special Issue. Citizen Science — new pathways to public involvement in research. Frontiers in Ecology and the Environment. Vol. 10(6). August.These contributions have not been peer-refereed. They represent solely the view(s) of the author(s) and not necessarily the view of APS.