Why Light Pollution is Harming Tropical Forest Regeneration

Light pollution is a real thing that we should all be concerned about. Far from just being aesthetically displeasing, light pollution has been shown to have serious detrimental effects on nocturnal life on this planet. By blotting out the stars with night lights, humans are depriving many organisms the cues they need for activities such as navigation and breeding. It doesn't end there either. A 2014 paper published in the Journal of Applied Ecology has shown that light pollution is impairing rainforest regeneration.

How is this possible? Surely the light produced by man at night is not significant enough to affect photosynthesis and germination, right? The answer may not be as straight forward as one may think. The truth is, in many parts of the world, bats are important pollinators and seed dispersers. In the tropics, they are some of the only animals that will disperse seed (via their guano) into cleared patches of forest.

Researchers have found that when exposed to light, especially the kind used to light streets, buildings, and houses, bats were significantly less likely to spend time in those areas. This means less foraging and fewer seed dispersal events. Basically, as humans expand into these forested habitats and begin lighting up areas at night, fewer bats hang around and the forests suffer the brunt of this absence. As light pollution increases across the globe, I am sure that more and more of these types of relationships will be disrupted.

Photo Credit: Katja Schulz (http://bit.ly/1fou0OY)

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Snuffing the Fire

Few childhood memories are more fond to me than catching fireflies on summer evenings. These little beetles are famous the world over for their dazzling light displays. Using chemical means, they are some of the most efficient light producers ever discovered. Their displays are for the purpose of mating and there are as many variations on the theme as there are species. Sadly, like so many natural wonders that we take for granted, fireflies are disappearing from our wild places. Future generations may never know the joys of these natural fireworks. 

Exactly why we are seeing a decline in fireflies is not certain. Researchers are only just beginning to uncover the secret world of the firefly. The answer is undoubtedly complex, however, evidence is beginning to pour in that we should look no farther than ourselves for the cause.

Fireflies require a few things to get by. The first is some sort of standing water. They seem to love ponds, creeks, rivers, and vernal pools. Second is tall grass and a lot of forest litter. Their larvae live and hunt in and amongst fallen logs and plant litter. Though we aren't entirely sure what their larvae eat, they are certainly hunting things like snails, slugs, and small insects, which also require moist areas with a lot of debris. Fireflies also need taller plants like grasses. They will climb up the stems to begin their aerial light displays. Finally, fireflies need darkness. They communicate by light and any surplus light sources are likely to mess them up. 

With increasing human development, former firefly habitat is giving way to paved roads and chemical laden lawns. Mowers run endlessly during the summer, eliminating fireflies and their habitat. People are needlessly clearing land of brush piles and fallen logs, which their larvae as well as their prey need. Light pollution is only getting worse too. As with many other insects, the wanton use of insecticides are undoubtedly taking their toll as well. Areas that once harbored huge populations of fireflies are quickly becoming overrun with human traffic as new housing, commercial and other forms of development garble up what free land remains. 

At this point you may be wondering what you can do to help. If you are a land owner, please consider the following:

- Turn off outside lights at night when they aren't needed
- Let logs and other plant debris accumulate in places around your property
- Consider creating a water feature of some sort
- Avoid the use of pesticides and fertilizers on your lawns
- Plant native plants
- Don't over-mow your lawn and leave some areas un-mowed

The best part about these solutions is that they benefit so much more than just fireflies. Native wildlife will be all the better if you take these steps to making your property more ecologically friendly. We are lucky to be aware of this issue but we must take matters into our own hands. Get out there and enjoy nature and try to be a bit of steward at the same time. 

Photo Credit: Peilun Hsu (http://bit.ly/1rJkufG)

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