The UK government defines biodiversity as “the variety of all life on Earth: genes, species and ecosystems” which appears to be a simple overarching definition but quickly becomes contested by scientists for the ways in which we measure and value this variation. Some methods of measuring biodiversity are thorough but costly and others are more reliant on random sampling but are efficient. Money and time are not just a concern, but also how biodiversity should be preserved to maximize conservation efforts. This has led to debates over whether rarer species, keystone species, or just a lot of present species has greater value to the ecological system. Regardless of the ways in which you value or measure the biodiversity of your chosen study sites, there are lots of different ways to do so. This is an important methodology to consider for any undergraduate studies that you may want to develop all the way into a PhD thesis or a methodology to learn so you can provide vital insights to environmental health consultancy firms or local government projects.
Methods:
Quadrats are a very simple methodology which involves drawing, usually, a square around a study site and counting the species within the site. This can be done on a small scale at 1 meter squares all the way up to large scale projects of 1 kilometer squared. It’s a relatively cheap measure, but relies on the researcher having a skilled knowledge of species identification and can be time consuming.
Similar to quadrats, transects can be erected very simply on a small scale to larger scale projects. This method involves drawing a line along a study site and taking measurements along the line. This is often used to measure species gradients. Again, it is simple and cheap, but it may take a long time to identify every species along the transect in the field.
Remote sensing can be conducted using high resolution satellites for large scale studies or in conjunction with an aerial flyover methodology which uses drone cameras for species counts. Both technologies may rely on just the human eye for counts or can utilize thermal cameras and tracking to capture the individual heat signatures of different species. These methods are useful for conducting counts in dangerous terrain or at night. Both can be tedious to use, but are often the only option for the aforementioned circumstances.
This may be a methodology that you’ve encountered in your everyday life if you’ve ever seen tagged animals while walking around outside. Marked catch and release involves capturing a subject and tagging them to track their movements and behaviors or to ensure that they are not double counted. This is useful for more longitudinal studies. Shorter studies may employ catch and release without tagging through forest animal traps, cups to catch bugs, or fishing. The ethics of this method are often debated, but it is still useful for measuring individual subjects.
When visual species counts cannot be utilized for one reason or another, like time constraints or safety, different types of indirect counts can be used. This can be methods like counting scat or animal tracks or setting up audio recorders. These counts are relative, but are useful when other options aren’t available and provide unique data that can give insights other than just counts.
Quantitative Measures of Diversity:
After collecting raw data in counts by species, these measures and transformations help to interpret and standardize the data.
Richness is the amount of species present and helps to capture their variety.
Abundance is the amount of individuals which helps to understand the population of the study site.
This is the abundance per every species type which helps to quantify dominance and competition in the sample.
Sometimes more complicated calculations called indices are used to combine all of the above factors:
The Shannon Index uses this formula: H = -Σpi * ln(pi) to calculate the evenness of a community.
The Simpson index uses this formula: D = Σni(ni-1) / N(N-1)to calculate the likelihood of picking two species from the sample that are the same which gives more weight to dominant species.