We hear a lot about habitat loss, but what does that mean for pollinators? And what, if anything, can be done about it?
Habitat loss comes in many forms, but it can be divided into three major types: habitat destruction, habitat degradation, and habitat fragmentation. Let’s look at these one by one.
Three types of habitat loss
Habitat destruction is very much like it sounds: an ecosystem, which is a naturally-occurring assemblage of plants and animals and their physical environment, becomes obliterated. If you take a wild meadow, for example, cover it with asphalt and erect a shopping center, you have destroyed any trace of the natural environment and all the things that once lived there. Obviously, this is not good for pollinators nor any other living thing.
Habitat degradation is a reduction in the quality of an ecosystem. In other words, the land may still look like a wild land or a place where pollinators might live, but closer inspection will reveal that things aren’t quite right. An example is invasion by non-native plant species. If an area becomes overrun with say Japanese knotweed, kudzu, or Scot’s broom, the native plants gradually disappear. The native plants cannot compete with some of these invaders for sun, nutrients, water, or space. When the native plants disappear, the animal species that were dependent on them disappear as well.
Other things besides invasive plants can degrade a habitat. Industrial pollutants, pesticides, excessive shade or excessive sun, water diversion, or grazing animals can all degrade a habitat to the point that some of the original species can no longer survive.
The last one, habitat fragmentation, is perhaps the most insidious because it is deceiving. Habitat that is fragmented may look perfect, may have all the original components and none of the bad ones, but still be unfit for certain species to survive. How does that work?
An imaginary town
Let’s invent a town that is perfectly square, a mile per side. A square mile contains 640 acres. The developers of this town were forwarding-thinking individuals who decided to put a natural preserve at each corner of the town. Each preserve is 20 acres and left in a natural state. Sounds nice.
But these 80 acres are fragmented—fragmented because they are cut off from each other. Now, for some species this is okay. Even for honey bees this is okay, and maybe even bumble bees. Honey bees and some bumbles can cover the distance between the four preserves.
But for most bee species, this is a serious situation. Most bees can travel only a few hundred yards from their nest, so in small isolated areas like this, the species become inbred. The bees living there are cut off from the larger pool of genetic material because the only bees to mate with are the ones already there.
It doesn’t happen instantly, but when you have small, isolated, in-breeding populations, “bad genetics”—usually in the form of double recessive genes—begin showing up. Genetic problems arise more frequently in a closely-related population because there is a limited number of alleles (genetic variations of a gene) available. The situation only gets worse if no new blood is coming in.
If an inbred population is then confronted with an unusual circumstance, it may not have the genetic variability to survive. Unusual events like drought, extreme cold, a disease, or a new parasite may wipe out the entire population because it didn’t contain enough genetic variation to assure some survivors.
What island biogeography tells us about fragments
The study of island biogeography illuminates what happens to fragmented populations. Island biogeograhers examine populations that are cut off from each other. Remember Darwin’s finches? They presumably got dispersed to different islands, blown there by storms, and once there, each population developed different kinds of beaks because the food sources were slightly different.
That was a good result of separation, but more frequently the results are not so good. Small populations cut off from larger ones often do not survive.
From an evolutionary point of view, habitat fragments are like islands and the same processes affect them. Today, ecosystems everywhere are fragmented by cities, roads, airports, housing developments, farms, and industry. Fragmentation can even affect migratory animals like butterflies and birds because the fragments may be so far apart that the animals cannot find sufficient food or safe resting areas.
Wildlife corridors and how you can help
Maybe you’ve heard the term “wildlife corridor.” A wildlife corridor is a method of connecting various natural areas so that individuals can freely travel between them and encounter a larger selection of mates. Utility easements, for example, can be used as corridors by simply leaving them natural.
Individuals living in cities and suburbs can build corridors by planting wildflowers, keeping pesticide-free gardens, planting trees, and leaving a few weedy patches and some bare ground for the pollinators to use. While a single flower pot or a few milkweeds behind the garage may seem insignificant, they can make a huge difference. They give pollinators a way to connect with others, travel safely to other areas, and expand their genetic resources.
So do your part and plant that flower pot with something that blooms. Your pollinator friends will be glad you did . . . and so will you.
Honey Bee Suite