Monday, May 16, 2016

Early Spring Pollinators and their Flowers

Bluebells and carpenter bee
© Beatriz Moisset

Many gardeners are developing a new concern for pollinators. They look for ways to help them. Aware that a perfectly manicured, pesticide-laden lawn is not good for pollinators they enthusiastically adopt a scattering of dandelions in the early spring.

This is certainly beneficial to pollinators. However some of the passionate claims that accompany this activity are somewhat exaggerated. It is not true that pollinators “need” dandelions. They would prefer other flowers if they had a chance.

Spicebush in bloom
© Beatriz Moisset
Spicebush and pollinator
© Beatriz Moisset
Before dandelions were introduced from Europe and before lawns became so rampant in our suburbs, early spring pollinators were faced with a smorgasbord of early spring flowers. Here is an incomplete list of the so-called spring ephemerals prevalent where I live, in the Mid-Atlantic region: spring beauty, trout lily, trillium, columbines, rue anemones, Dutchman's britches, bloodroot and bluebells. These and others can still be found in nature areas, although they have become extremely rare in gardens and parks. Perhaps even more important to early spring pollinators are a number of trees and shrubs, such as willows, maples (some, not all of them), serviceberry, sassafras, spicebush, redbud, and a little later, azaleas and dogwoods, just to name a few.

Spring beauty and spring beauty Andrena
© Beatriz Moisset
This assortment of flowering plants offers a rich and diverse diet to newly awakened queen bumble bees, early Andrena bees, and other bees and flies seeking pollen and nectar. Some pollinators are specialists on just one or a limited variety of flowers. The spring beauty Andrena, trout lily Andrena and several willow blossom devotees would look at dandelions in despair, not being able to make any use of them.

Trout lily, frequently visited
by the trout lily Andrena
© Beatriz Moisset
The biotic community described above not only nourishes early-riser pollinators but also provides food and habitat for local wildlife. For instance, the red maple serves as a host plant for more than 100 moth species, willows provide food for several hundred species of moths. In turn, these caterpillars nourish birds and other wildlife. By contrast a lawn with dandelions is an impoverished ecosystem with very limited ecological value, more similar to a refugee camp than to a healthy, lively community.

Azalea and its specialist
the azalea Andrena
© Beatriz Moisset
If the goal is to help pollinators we would reduce the size of the lawn and grow some of the plants mentioned above rather than simply allowing dandelions among the blades of grass.

Bloodroot and Red-necked False Blister Beetle
© Beatriz Moisset
Such a goal is hard to achieve for most gardeners and probably impossible or nearly impossible for many of them. So, reducing the use of pesticides and allowing dandelions, as well as a few other small lawn “weeds,” is a good decision. But anybody seriously committed to protecting, not just pollinators, but entire ecosystems would do well to take a look at other alternatives.

Dandelion visited by a cuckoo bee
© Beatriz Moisset
Dandelion and ants
© Beatriz Moisset

Wednesday, May 11, 2016

Too Much Light!

Outdoor light
Most of it is wasted, aiming to the skies
© Beatriz Moisset

Could it be that we have too many outdoor lights? Night lights have become so abundant that they can be seen from space. Large cities are beacons made of myriads of tiny dots of light. The planet has never seen anything like it before. We know the benefits of good illuminated streets and public areas. Could there be some drawbacks too?

For one thing, we have lost the ability to see the night sky in all its splendor. Most stars have become invisible to city dwellers. Even in the suburbs and some distance from large cities, lights affect our vision of the sky. Astronomers regret this deeply and have some suggestions on how to mitigate the impact of night lights.

Night lights have other effects worth discussing. We all know that moths are attracted to lights. We often see a handful of them flying aimlessly around our porch lights or finally settling on a wall for the rest of the night. They are still there the next morning and remain still for the day since they are not day fliers.

How does this affect moths? Undoubtedly, such behavior may cost some of them their lives by exhaustion and lack of food. Does it matter?

Many moths are pollinators of night flowers. Nature is rich in its approaches to issues. Although most flowers bloom and are pollinated during the day, preferably when the sun is shining, a few take advantage of the darkness of dawn and dusk and even the middle of the night. Thus, they take advantage of certain flower visitors that have developed a similar strategy, namely being active at night.

Thyatira lorata moth
Attracted to night lights and
spending the day where it finally rested
© Beatriz Moisset
This is how a partnership has developed between some flowers and nocturnal moths. Ordinarily, such flowers are white or cream colored and have strong scents, better to attract their pollinators. Moths, in turn, have good night vision and a strong sense of smell.

Getting back to light pollution, if it kills moths, it too may be affecting the pollination of night blooms. We don't know this for sure, but there are strong indications that this is the case. Also some evidence points to night lights affecting the growth of some plants by getting their schedule confused.

We should follow the suggestions provided by several websites on how to minimize light pollution, for instance the Florida AtlanticUniversity website covers a lot of ground. One useful recommendation is "no light should be emitted above the source's horizontal plane."

The Mother Nature Network lists five ways you can reduce light pollution:
  1. Start with the light switch
  2. Check with your power company to see if you're paying for outdoor lighting
  3. Consider replacing outdoor lights with intelligently designed, low-glare fixtures
  4. Place motion sensors on essential outdoor lamps
  5. Replace conventional high-energy bulbs with efficient outdoor CFLs and LED floodlights
However most of these ideas, although excellent provide no significant protection to pollinators and their plants. For this purpose one valuable tip is to abstain from lighting the landscape. There is no real need to illuminate your trees, shrubs and the general area where they grow, so let us give up this kind of lighting, please.

Virginian tiger moth
© Beatriz Moisset

Friday, May 6, 2016

The Most Invasive Butterfly: Cabbage White Butterfly (Pieris rapae)

A flock of cabbage butterflies
(Pieris rapae)
© Beatriz Moisset
If you see a pretty white butterfly, more likely than not you are seeing an invasive species that was accidentally introduced to this country and to many other parts of the world more than a century ago.

The cabbage white butterfly is noticeable, pretty and soft, it visits gardens, meadows, you name it. Perhaps the only places beyond its reach are higher elevations. It starts flying early in the season and produces several generations throughout the summer and fall. No wonder it is seen so often.

Cabbage butterfly
(Pieris rapae)
© Beatriz Moisset
The name refers to the plant its caterpillar feeds on, cabbage. It also eats other members of the mustard family, such as cauliflower and kale and it is regarded as a serious pest. It also feeds on a number of wild, non cultivated mustards, including the invasive garlic mustard.

The cabbage butterfly is related to a group of native butterflies, the so called whites, yellows and sulphurs or family Pieridae. Their colors, as the names indicate are either whites or yellows. The caterpillars of most of them also feed on plants of the mustard family. A total of 58 species lived in North America before the arrival of this newcomer. Nowadays, the cabbage white is seen as often as all of them combined. One wonders if the growing numbers of this invader are having an impact on the populations of native Pieridae butterflies.

Orange sulphur butterfly
© Beatriz Moisset
In summary, it has the qualities of so called weedy species, with high rates of reproduction, very adaptable to different food sources and a variety of habitats.

Virginia white butterfly
Pieris virginiensis
© Beatriz Moisset
The cabbage butterfly reminds me of several insect species that were brought to this country intentionally or accidentally and proceeded to become incredibly widespread in a relatively short time. Now, some of them are more abundant than any of their native relatives. Here are a few examples: the Asian ladybug, the Chinese mantis, the giant resin bee, the European paper wasp, the drone fly, and the brown marmorated stink bug.

David Quammen, a distinguished journalist who has written extensively on conservation and ecology, has coined the term “Planet of Weeds,” meaning that the ecological changes caused by humans are having a severe impact on the flora and fauna of the entire planet. We had transported unprecedented numbers of species of plants, animals and bacteria beyond their natural distributions with the consequence that many of them have become established in their new surroundings. Not only do they become established but spread out from the original place of introduction, thus deserving the name of invasive species. They impact the local flora and fauna, bringing up the extinction of many species. In this way we are causing a mass extinction, comparable to some of the most serious mass extinctions of the past.

Specialist species are more vulnerable to extinction. The ones that have the best chance for survival are the weedy ones, the adaptable generalists. We are creating an impoverished world, gradually losing precious biological diversity, biodiversity for short. It may take millions of years for this biodiversity to raise back to the present levels. The human species may never see that.

Drone fly (Eristalis tenax)
One of many introduced, widespread species