A bioblitz is a 24-hour survey of the taxa in a defined area.

Teams led by experts in different groups of living things survey to find as many different species as possible during that time.  These are fun events to take part in.  Participants learn of different groups of organisms that are present and different survey methods used for different groups.  Anyone interested in nature or biology is likely to have a valuable experience at a bioblitz, even if it is only to talk to the biologists as they tally their finds.

The result of a bioblitz survey is a list of species from many different taxa that may be used to inform the public of the biodiversity in their local area or may set a baseline of species present in the area.  It may be tempting to use the resulting data to compare the abundance or diversities of taxa in different areas that are surveyed or even the same area surveyed in different years.  However, this is usually not a valid comparison for two main reasons: 1) many conditions that are not the focus of the comparison will be different, and 2) the effort is not standardized.  The first of these two issues is related to a major aspect of the scientific method, and the second to a common aspect of ecological studies.

In a scientific study it is important to control any potential confounding influences.  It would be incorrect to compare the results of bioblitz events at a more northern and more southern area, perhaps to determine which area had a greater number of scarab beetles, and then assign any observed difference to latitude.  Various other factors will also differ between the two sites, such as habitat, habitat amount, climate, disturbance, and water chemistry, any of which may have an effect on the different species.  Ideally, as many of these characteristics would be controlled as possible so that more of the difference in scarab beetle communities could be assigned to latitude.

The issue of standardization of survey effort is a common one in ecological studies.  Great attention must be paid to ensuring that the same effort is used in surveying each study area, or sometimes that survey effort scales with the area surveyed.  Obviously more individuals are found with a longer search, and more species are thus found.  The nature of a bioblitz survey is usually not conducive to rigorous standardization of effort.

However, it is also important to consider effort even when simply comparing the presence or absence of a single species.  Regardless of how easy or difficult a species is to detect, there is a probability of detection given that the species is present.  If the species is found at both sites, the conclusion is obvious.  However, if it is not found at a site, the surveyor cannot know with certainty if it is absent or if it was present but not seen.  Simply put, it is easy to prove the presence of a thing, but it can be difficult or impossible to prove an absence.

Given that the results of bioblitz events do not lend themselves to comparison, why are they carried out?  These events can be valuable for several reasons.  One important thing that a bioblitz can do is educate the public about the vast diversity of things living right in their neighborhood.  The first step to appreciation is identification.  People will be less likely to be interested in something living in their local environment if they don’t even know what it is.  The second valuable contribution of a bioblitz event is the resulting presence data.  The first time a species is found in a county or state/province, termed a “new county record” for example, represents a valuable datum point.  As species respond to changes in land use and the climate the geographical range they occupy changes.  Data on the presence of a species or group, even without reliable absence data, allows scientists to track these changes.  The value of bioblitz events thus lies in informing the public and perhaps changing opinions towards nature, and informing science on a global scale—lofty outcomes from a fun weekend activity.