What is biodiversity and why is it essential?
In everyday language, biodiversity refers to the number of species that exist in a given area. Although this statement isn’t wrong, biodiversity is actually a much more interesting and complex topic than that.
If biodiversity isn’t simply the number of species in an area, what exactly is it then? Answering this seemingly simple question turns out to be an arduous task!
Consider the following:
Two communities (we’ll call them community A and B) each have 16 individuals from four different species. However, community A has 13 individuals from one species and only one individual from the other three species, whereas community B has four individuals from each of the four species. Are these communities the same? Clearly not, but our initial definition would not be able to distinguish the two!
The concept of biodiversity thus has two components: species richness and species evenness. Species richness is the number of species in an assemblage whereas species evenness is the relative abundance of each of these species. Ecologists have developed a number of equations to measure these factors to obtain diversity scores (see Simpson’s and Shannon’s diversity indexes for examples).
There’s more though.
Let’s take a look at another scenario with this simple example:
Again, two communities (community X and community Y) both have 16 individuals from four different species. Community X consists of four species of songbirds whereas community Y is made up of a tree, a songbird, a mammal, and a fungi. Here, the two communities are mathematically equivalent even though they are in no way ecologically similar!
That is why many ecologists will also use functional diversity―this assigns biologically relevant roles to separate the life forms into groups instead of relying on species count. In the above example, we will set our categories as producer, consumer, predator, and decomposer although any categories could be used. All the organisms from community X now fall into a single category where community Y still has 4 individuals in each of the 4 categories.
And yes, it gets more complicated than that (biomass, genetics, etc) but we will leave it here for this post.
So what is the best diversity measure to use?
A definite answer does not exist. It requires that we use discretion and careful planning to apply the best method to the problem we are trying to address.
Why is biodiversity so important?
The popular answer is a utilitarian one―species hold biological secrets that we can use to create medicines to cure diseases. For example, a popular medicine to cure hypertension comes from the venom of a snake native to South America. Evolution is by far the greatest problem solver of all time and the innumerable species that evolved over millions of years are a vast repertoire of biological knowledge we can use. However, we’ve only explored a small portion of the world’s biodiversity; if we cause species to go extinct, we may never discover these beneficial remedies.
Another reason to value biodiversity is because habitats become more resilient with increased biodiversity. Take the following example: A pure stand of ash trees and a forest composed of 4 species of equally distributed trees (ash, maple, pine, and beech) both get affected by a deadly outbreak that kills the ash trees. The pure stand dies out completely whereas only 25 percent of the trees die within the mixed forest allowing the remaining trees to keep producing food and supporting life.
Biodiversity is also important because it means more specialization in organisms which leads to better resource use. Imagine a market made up of only unskilled workers. It would not be very effective. There would be no one to program software, build houses, communicate ideas effectively, set up the power grid, entertain people, etc. Additionally, all the workers would compete for the same easily accessible jobs. The same phenomena applies with lifeforms: Instead of competing for the same habitat, species evolve to specialize in their own niche: One species of tree will specialize to grow on sand while another to thrive in wetlands. Furthermore, species will evolve ever finer ways to obtain resources: Instead of fighting for the same insect, one bird will evolve a wide beak to catch insects in mid-air while another an elongated beak to probe for them beneath tree bark. If we lose one of these species, there will be no more predators to keep those hard to catch insect populations in check. Maintaining biodiversity thus prevents homogeneity and inefficiency.
If biodiversity isn’t simply the number of species in an area, what exactly is it then? Answering this seemingly simple question turns out to be an arduous task!
Consider the following:
Two communities (we’ll call them community A and B) each have 16 individuals from four different species. However, community A has 13 individuals from one species and only one individual from the other three species, whereas community B has four individuals from each of the four species. Are these communities the same? Clearly not, but our initial definition would not be able to distinguish the two!
The concept of biodiversity thus has two components: species richness and species evenness. Species richness is the number of species in an assemblage whereas species evenness is the relative abundance of each of these species. Ecologists have developed a number of equations to measure these factors to obtain diversity scores (see Simpson’s and Shannon’s diversity indexes for examples).
There’s more though.
Let’s take a look at another scenario with this simple example:
Again, two communities (community X and community Y) both have 16 individuals from four different species. Community X consists of four species of songbirds whereas community Y is made up of a tree, a songbird, a mammal, and a fungi. Here, the two communities are mathematically equivalent even though they are in no way ecologically similar!
That is why many ecologists will also use functional diversity―this assigns biologically relevant roles to separate the life forms into groups instead of relying on species count. In the above example, we will set our categories as producer, consumer, predator, and decomposer although any categories could be used. All the organisms from community X now fall into a single category where community Y still has 4 individuals in each of the 4 categories.
And yes, it gets more complicated than that (biomass, genetics, etc) but we will leave it here for this post.
So what is the best diversity measure to use?
A definite answer does not exist. It requires that we use discretion and careful planning to apply the best method to the problem we are trying to address.
Why is biodiversity so important?
The popular answer is a utilitarian one―species hold biological secrets that we can use to create medicines to cure diseases. For example, a popular medicine to cure hypertension comes from the venom of a snake native to South America. Evolution is by far the greatest problem solver of all time and the innumerable species that evolved over millions of years are a vast repertoire of biological knowledge we can use. However, we’ve only explored a small portion of the world’s biodiversity; if we cause species to go extinct, we may never discover these beneficial remedies.
Another reason to value biodiversity is because habitats become more resilient with increased biodiversity. Take the following example: A pure stand of ash trees and a forest composed of 4 species of equally distributed trees (ash, maple, pine, and beech) both get affected by a deadly outbreak that kills the ash trees. The pure stand dies out completely whereas only 25 percent of the trees die within the mixed forest allowing the remaining trees to keep producing food and supporting life.
Biodiversity is also important because it means more specialization in organisms which leads to better resource use. Imagine a market made up of only unskilled workers. It would not be very effective. There would be no one to program software, build houses, communicate ideas effectively, set up the power grid, entertain people, etc. Additionally, all the workers would compete for the same easily accessible jobs. The same phenomena applies with lifeforms: Instead of competing for the same habitat, species evolve to specialize in their own niche: One species of tree will specialize to grow on sand while another to thrive in wetlands. Furthermore, species will evolve ever finer ways to obtain resources: Instead of fighting for the same insect, one bird will evolve a wide beak to catch insects in mid-air while another an elongated beak to probe for them beneath tree bark. If we lose one of these species, there will be no more predators to keep those hard to catch insect populations in check. Maintaining biodiversity thus prevents homogeneity and inefficiency.