The largest organism in the world is in Eastern Oregon. It is a networked mycelium that measures 2,400 acres and is 2,200 years old. Mycelium is the network of branching hyphae that serves as the root system for fungus. Mycelia (the plural of mycelium) are all over the world, on land and in water. They actually break down nutrients from their surroundings and transport those nutrients along their networks to mushrooms and other plants. Mycelia are good candidates for polluted soil remediation because they break down pollutant molecules and displace salts. This is a fine topic for audiences who like biology, ecology or science.
This one is an eye-opener because it has some profound implications for modern lifestyles in the not too distant future. Current food and transportation systems are absolutely dependent on oil, for which no viable substitute is on the horizon at the scale necessary to replace it. The problem is, oil is a finite resource, and extracted resources typically go through two "peaks": a discovery peak and a production peak. After the production peak, the amount produced goes into terminal and irreversible decline. World oil discovery peaked in 1965 and has dropped steadily ever since, even as demand and production has increased. Many scientists estimate the world is at peak production now, and facing an inevitable and permanent production decline in the immediate future. Estimates vary, but the broad numbers are an attention-getter as a speaking topic.
Crime whodunits, like the immensely popular "Law and Order" television series, have given many people the impression that eyewitness testimony in court is the be-all and end-all of evidence. In actual court situations, eyewitness testimony is one of the most compelling kinds of evidence for juries. Research, however, suggests that eyewitness testimony may be one of the least reliable kinds of evidence. Psychologist Barbara Tversky has done extensive research on memory fallibility, and she found that not only can things be "placed" into memory by a simple word or suggestion, but also that day-to-day memories are distorted by the telling of them. Oftentimes people can describe a memory that is embellished in the description, then the embellished version is what is "remembered." The judicial system's reliance on eyewitnesses may be misplaced.
People are often fascinated by nutrition. After all, it affects everyone's health and well being. Try speaking about the topic of "super foods." Super foods are foods that do nutritional multitasking when eaten. They provide energy, vitamins, antioxidants and other benefits in dense packages. There are lists of super foods available online, and each is its own subtopic in reviewing its virtues. Aliums, barley, beans, buckwheat, hot peppers and yogurt make most of these lists.