Before I discuss the results of recent studies on the efficacy of zoos/aquariums on visitor education, I would like to briefly outline some of the focuses and potential outcomes on each of these three goals.
Zoos aim to meet conservation goals through several means.
1)Zoos are often considered as a "biological ark," that can maintain a population of animals that may be declining in captivity. Thus, their goals are, ostensibly, to maintain a captive population to prevent total extinction, as well as to provide a source population for re-introductions. However, there are some obstacles to achieving these goals. The small populations are at risk for inbreeding. Though zoos usually carefully manage breeding with the goal of maintaining genetic diversity, they may be constrained by the amount of genetic variability within the existing captive population, as well as space constraints that limit the amount of animals that can be maintained within the zoo system (for the US, this would be the AZA). Furthermore, while there have been some succesful reintroduction projects, reintroduction is difficult to do (especially for primates and other social animals). This may be because animals may be have lost crucial survival skills, or because of the risks of introducing disease to wild populations.
2)Coordinating and funding field conservation efforts. This is probably the most crucial contribution that zoos make toward conservation. By raising money for field conservation, and funding field projects (or in some cases, coordinating field projects themselves, for example, see Lincoln Park Zoo's conservation projects). In particular, I am a big fan of zoo exhibits that provide a link between their captive animals and their habitat in the wild, and specifically encourage donations toward that end.
1)Zoos seek to educate the general public through informing visitors about conservation crises, and inspiring them to care enough to become involved through donations or other means. Furthermore, they provide education material on specific animals and habitats, to increase visitor's knowledge base about animals and their habitats. Ultimately, the idea is that if people feel a connection or empathy for the animals, they will feel motivated to take greater efforts toward supporting conservation, through moderating their environmental impact, participating in local conservation efforts, and donations to field conservation funds. This is particularly important for children, as they often spear-head family changes--for example, the recycling movement largely grew through schools developing recycling programs, and educating children on the importance of recycling; the kids in turn, encouraged their parents to recycle. Children also represent the next generation of potential conservationists.
1) Zoo populations provide opportunities for many different avenues of research. In particular, the genetic research and management of small populations is crucial for maintaining genetic diversity of zoo populations themselves. However, this research is also helpful in learning to manage and conserve diversity in wild populations, that are often increasingly fragmented and isolated.
2)They provide observation and sampling opportunities for topics that may not be feasible in the wild (for example, projects that require close-range observation, or fecal sampling that may not be possible in the wild--for example, fecal samples collected from the spider monkeys at Brookfield Zoo before and after a stressful experience-a vet exam-are essential to my pilot research).
3)Finally, zoo research is crucial in monitoring the welfare and health of the animal themselves, and in making modifications to promote welfare.
However, while a number of zoos have active research programs, I think that they are often an untapped and underutilized resource. Unfortunately though, gaining permission to conduct research at zoos (even just observational research from public observation areas--gaining access to non-public areas or fecal samples can be even more challenging), often requires jumping through hoops, or having connections within the zoo. This varies widely, but some zoos are not that supportive of facilitating outsider research (as with jobs in the zoo world, having connections within the zoo world often makes a difference).