The 17 Year Itch

That sound you hear isn’t the Six Million Dollar Man using his bionic powers. It’s cicadas by the billions. Every year, at least a few cicadas emerge during late spring and serenade us with their mating call. Chunky and scary looking, these insects are totally harmless but to me at least, just hearing them makes it feel a little hotter and muggier. 

This year is a little louder than most. Brood X, the largest brood of periodical cicadas, is emerging after 17 years underground in the larval stage. They’ve been tapping into tree roots during that time and now that they’ve reached adulthood they’re ready to go out in a blaze of noisy glory. They'll mate soon, lay their eggs in the tree tops, and die. When the eggs hatch, the larval cicadas will drop from the tree, burrow into the ground, and start the timer on another 17 years.

Expect it to be a little louder than usual in the Northeast
(From "This Is Spinal Tap")

All those bugs means not just a lot of noise, but also a lot of food for just about everything. The reason cicadas emerge by the billions is to overwhelm their predators’ stomachs. The strategy is that lots of cicadas will get eaten, but based on sheer numbers, many will survive to continue the life cycle for another 17 years. 

Periodical cicada (NPS)

Speaking of 17 years, why such an odd number? It’s another evolutionary strategy. What other critter can you think of with a 17 year life cycle? It reduces the risk of broods emerging during a population boom for a predator species. As a double failsafe, broods have stragglers that emerge either before or after the 17 year period.  Most are within a 13 to 21 year period. It gives the brood a better chance of survival in the event that the 17th year is a boom year for predators. 

Molting cicada (Baltimore Sun)

I've never seen a cicada coming out of its shell. Like all insects, they have a hard exoskelton, and immediately after emerging they molt. From what I'm being told, people all over are finding a lot of those shells on tree trunks and other surfaces. I haven't seen any yet this year, but I haven't been able to get outside much other than a birding expedition to New Jersey which you can read about later. This week's information comes from the University of Connecticut. 

Wind Energy

Wind energy is another “clean” energy using the power of moving air to generate electricity. It is renewable because there is no shortage of air on the planet, and it is constantly in motion to a varying degree. It is not completely reliable because the wind is not always blowing, although the wind turbines are at least 100 feet above the ground to take advantage of the less turbulent and more abundant airflow, as compared to ground level.

Wind farm (US Department of Energy)

Wind energy currently makes up 4% of the US energy mix, but is growing and will eventually pass
hydroelectric as most rivers are dammed to capacity. An ideal place for wind farms in the central US
“Tornado Alley” because of nearly constant strong wind. Wind farms are compatible with the
traditional farms of the region and are an economic boon for farmers. They can lease land to energy
companies for windmill placement, and still have the ability to use nearly all of their land. Ridge tops
in the Appalachians are another great location, where topography produces adequate wind speeds.  

Developing technology has greatly improved the efficiency of windmills. Lighter blades, taller towers,
and control systems have increased the average capacity factor from 22% in 1998 to 33% in 2014. As
the race to replace fossil fuels continues, expect efficiency to increase further.

The downside to wind energy, aside from lack of wind, includes environmental impacts. Construction
of windmills in undeveloped areas requires access roads and site preparation, which can be a strain on
the environment. Leaking lubricants can pollute the soil. Birds and can be struck and killed by
windmill blades. However, fewer birds are killed by windmills than stationary buildings. Many birds
are learning to avoid areas containing windmills. Tornado Alley windfarms are away from major
flyways so migratory birds are less likely to affected in that region.

Birds and windmills are not always a good mix (NBC News)

Other negatives are aesthetics and safety. Many people believe the windmills are unsightly and ruin the
landscape. One workaround for that is to install them in developed areas, where they might actually
improve the view, especially if the view is mainly housing developments and shopping centers.
The focus then shifts to noise. The rotating blades can be noisy, depending on the distance from the
listened but the elevation above the ground helps reduce that.

Safety can be an issue when rotating blades are involved. Machines malfunction, and should a windmill
throw a blade, the potential for human death is there. A serious concern in Tornado Alley is that a
namesake tornado could destroy a wind farm and turn the blades into deadly projectiles.

This week's information comes from National Renewable Energy Laboratory, Mount Holyoke College, and US Department of Energy. Next week we'll take a look at solar energy.

Tidal Energy

Continuing the series on alternative energy sources, this week features tidal energy. It is similar to
hydroelectric power: it uses the same principles of water in motion and is also a “clean” energy source.
However, tidal power relies not on the temperamental flow of a river which is subject to effects of
weather and climate but on the timeless and ceaseless pull of the sun and moon on the world’s oceans.
Because of its reliance on ocean tides, this is considered a renewable energy source because it does
not diminish the amount of tides in the ocean.

Tidal power is also similar to wind power. Tidal turbines look like miniature underwater windmills.
Tidal turbines can be smaller and more densely spaced than windmills because water is denser than air;
less surface area is required to generate a comparable amount of electricity. While the wind may not
always blow, the tides are always in motion. 

Tide turbines (Forbes)

Another device to harness the energy of the tides is called a barrage. It is similar to a small submerged
dam that blocks the incoming and outgoing tides at the mouth of an estuary. A sluice in the dam opens
to collect the tidewater, which flows though and turns turbines to generate electricity.

One drawback of tidal energy is the tides themselves. Generation capacity is limited by the tidal cycle,
meaning peak demand will frequently be missed. Also, the change in tides must be at least seven
meters for this to be economically efficient. 

Barrages are limited by location. Not all estuaries are suitable sites. The equipment used for generation (either barrages or tide turbines) must be highly durable due to the unforgiving nature of the undersea environment.

Tidal barrage (Britannica)

Like the other energy sources previously mentioned, tidal power has negative impacts on the environment. However, due to limit use of this technology, these impacts are still being studied and at present are not certain to be occurring. The possible impacts include altered waves, currents, substrate, and sediment movement; loss of habitat for benthic organisms; noise that may interfere with biosonar; generation of magnetic fields; introduction of toxins in paint, lubricants, and antifouling; hindrance of fish passage; and fish being struck by blades or sucked into turbines.

This week's information comes from Marine Current Turbines, Ocean Energy Council, and Pacific Marine Energy Center. After a brief break for a look at June's Species of the Month, this series will resume with wind energy.

Crickets

Fall has almost fallen. It's hard to believe summer was in full swing when you last read a fresh Nature Minute blog. Internet issues and life in general kept me from my regular schedule. Maybe where you are, the leaves are starting to turn, there's a bit of crispness in the air, mornings are full of fog, and nights are longer and full of chirping crickets.

Black field cricket Gryllus assimilis (Texas A&M) 

Here in Pennsylvania, crickets typically begin their nightly serenades in the late summer, continuing through the fall. Only the males chirp. They do so by rubbing their wings together, as a mating call for the females. They are most active at night, and even during daytime are hard to find. If they notice you getting close, they'll stop chirping so you really need to look hard if you want to find the source of the chirp. Warmer temperatures will produce more chirps, and the number of chirps drops with the temperature. I never counted chirps before, so I never noticed this.

Northern mole cricket Neocurtilla hexadactyla
(University of Florida)

Many people consider crickets to be a pest because the chirping gets annoying, but they are generally harmless. Since crickets favor loose soil, they are frequently found in flower beds, which are usually right under your bedroom window, giving you a front row seat. At the bottom of the food chain, in large numbers they have the potential to attract other unwanted guests to your home such as raccoons and spiders.

Carolina ground cricket Eunemobius carolinus
(Oklahoma Panhandle State University)

Nature Minute will return in October with more autumnal awesomeness. I'm taking a much-needed vacation. Until then, relax to the sound of the crickets. Don't let them drive you nuts. They'll only be around a few more weeks, and then it will be too cold to keep the windows open at night. This week's cricket facts come from Terro.

Sound of the Wild

Think about the sounds you typically hear over the course of a  normal day. It starts with the alarm clock and quickly fills with noise. The toaster, the hairdryer, the microwave, cars, cars, and more cars, people talking and shouting, buses, trucks, trains, planes, and of course your phone. If you're lucky you heard some birds singing on the way out the door. Other than the lawnmower, popcorn, and a log on the fire, my favorite sounds come from a land far from modern conveniences.
Next time you are out and about pay attention to what you hear. Insects buzzing, birds singing and calling, the wind in the trees (or your ears). In the mountains you might hear pikas and marmots barking, or larger animals like coyotes or wolves howling in the distance. In the fall, you might be treated to the eerie sound of bugling elk.

A not-so-distant coyote, not howling

Water is life, and it also provides a great soundtrack. I can listen to crashing ocean waves or a gurgling river all day long. Rain falling on surfaces other than pavement is a wonderful experience. The pattering on a tree canopy is soothing enough to forget about being soaked, and rain falling in a pond is a magical sound. In a naturally quiet environment like a cave, there's a good chance you'll hear only a single drop of water at a time, maybe a few seconds apart, maybe a few minutes. Even better than rain is the sound of thunder in the distance. This can be a bit worrisome if you're a long way from shelter.

The soothing sounds of the Firehole River

Late summer nights, if there is no thunder, fall asleep to the sound of the crickets. In the spring, fall asleep to the sound of the tree frogs. Another special spring sound, which I've only heard once, is the knocking sound the trees make after the thaw when they start absorbing water and their sap is flowing again. It took a while to figure that one out.

Pacific tree frogs, a sure sign of spring

Here is a link to a short video of some sounds recorded at Yellowstone National Park. Note that the pictures don't necessarily correspond to the sounds. See how many sounds you can figure out!

Do You Hear What I Hear?

Next time you head into nature, try to tune in to the sounds you hear. It can be hard to shut out the human world, especially in the urban wild. The sounds of nature can be quite soothing. I enjoy sitting by a river and listening to the water swirl over and around the rocks, each passing H₂O molecule making those rocks a little bit smaller and contributing sediment to the sea. I also enjoy the sounds of the sea: a chorus of gulls providing backing vocals to the endless roar of the ocean.

As relaxing as sounds may be for me, they are vital to the survival of the critters. Predators, especially owls, rely on the sound of their prey to find their next meal. Prey species rely on the sound of predators to make an escape. Both predator and prey use sound (among other signals) to communicate to each other. A whistling marmot might warn others of death from above, while the howling wolf warns others to stay away from the pack’s territory. Many different animals use sound to attract a mate.

Buzzing insects, bird song, and rolling thunder are all part of the natural soundscape. Like all things in the natural world, it is vanishing. Even in national parks, noise from traffic and the devises people haul into campgrounds drown out the natural soundscape. A hike into pristine wilderness, despite its seclusion, is not impervious to intrusion from commercial airliners passing overhead.

Song sparrow getting ready for his bug number

What does this mean for the critters? It’s too soon to say. A pair of National Park Service biologists are recording the soundscapes of our national parks as a catalog and for research. The goal is to find out of our noise is diminishing our enjoyment of the parks. I am willing to bet that the average person won’t even notice the noise we take into nature, but it’s a different story for the critters.

Kurt Fristrup and Bill McQuay capturing the natural soundscape of
Great Dunes National Park in Colorado

Another group of researchers is using sound recordings to determine the effectiveness of conservation projects. These researchers, working in Papua New Guinea (north of Australia), are trying to find a cheap and easy way to tell if their work is working. In a species rich ecosystem like a jungle, getting sound recordings of the many critters coming and going may be the answer. The monitoring system is relatively inexpensive and easy enough that the semi-primitive natives can do it, giving them a role in protecting the ecosystem around them.

Setting up acoustic monitoring in Papua New Guinea

Comparison between the soundscapes of continuous and fragmented
forest cover in Papua New Guinea

Next time you head into Nature, close your eyes and take a minute to listen to your surroundings. How many natural sounds do you hear, compared to man-made ones?

This week’s stories come from NPR (National Parks sound recording) and Cool Green Nature (Papua New Guinea research).