The availability heuristic according to Tversky and Kahneman states that events that are more easily remembered are judge as more probable than events that are less easily remembered.  One classic example in psychology will be the study on the prevalence cause of death. In the study, it was found that people perceive cause of death that leaves greater impression in people were perceive to occur more often. In the study, participants have to rate causes of death like automobile accidents and tornados more often than asthma and drowning. The reason for such a finding is because deaths from automobile and tornados usually make it to headline news, whereas deaths from asthma and drowning will not. Hence, people are often exposed to ideas of automobile accidents and tornados; they remember it more often and therefore recall them easier.

An example of such heuristic:

Which bird is more likely to be found sharing habitat with a polar bear?

□ Penguin

□ Swan

People will be more likely to pick penguin than swan their impression of seeing penguins in the cold polar regions, for example in the movie ‘Happy Feet’, more than swans and the similarity of habitat will lead people to choose penguin. But the actual answer is swan because penguins live in the Southern hemisphere, polar bears in the Northern hemisphere.

Generally the availability heuristic works well because it makes sense to have information that people needed often to be recalled easier as this increases the efficacy of people. But when it comes issues such as risk assessment, availability heuristic may pose more harm than benefit to use such a short cut. Taking Singapore as an example, the country seldom face health care issues such as viral infections. When the bird flu virus, H1N1 strikes Singapore, very few actually thought that they posses the possibility of being infected. But judging from the position of Singapore as a regional trade hub for south east Asia, the high volume of daily human traffic would subject the country to high likelihood of such infectious agent being transmitted from other countries.

The benefit that availability heuristic can be observed from the Dengue Campaigns in Singapore. The dengue outbreak was at its peak in 2005 and the resulted in 13000 cases reported for the year. As a result, campaigns were launched to educate the public on how to prevent the spread of dengue and how one can do to ensure that one’s household is not a cultivation ground for aedes aegypti mosquitos. The campaign proved to be a success as observed from the decrease in the number of reported cases of dengue in the recent years. 

An example of the steps taught to fight dengue:

 
Another Example:

Human dependency. from wrs_education on Vimeo.

This video not only made information regarding environmental issues more salient, it help to address the availability heuristics by putting information in short phrases that are easily understood and remembered. What I think was another success of the video was that it give viewers a concrete idea of what are the direct impacts that such issues have. It is another bias in humans to look at direct relationships in deciding the value of certain thing.
For example if you tell them that deforestation have a negative impact to the natural habitats of the native animals, they will be unable to relate it to themselves. But with what the video did,stressing on the direct impact of oxygen reduction and water catchment reduction, people can see the impact on themselves, without oxygen or with flood, they will be affected. With such information being brought across to them, it will likely increase salience and effectiveness of campaigns or efforts aim at addressing environmentally issues and of course availability heuristics because their attention will be focused on the information, leading to better encoding and retrieval of that information.