Written by Rhonda Kranz

Many people think only of allergies when they hear the word pollen, but pollen plays a vital role in the health of our environment, in agriculture, and in our aesthetic enjoyment of the world. Pollination is the transfer of pollen grains to fertilize the ovules – eggs – of flowers to produce fruit and seed. While some plants are self or wind pollinated, more than 70% of the world’s flowering plants rely on animals to transport pollen for them and more than 30% of the human diet is dependent on pollinators.

Pollinators come in all shapes and sizes. More than 200,000 invertebrates and 2,000 vertebrates serve as pollinators worldwide including insects, birds, mammals, and even reptiles. The co-evolution of these pollinators and their host plants is one of nature’s unique solutions to the dilemma of sexual reproduction.

Pollinators in Sligo Creek and our Neighborhoods

MD, VA, and DC are wonderful places to see pollinators in action. Just walk around the neighborhood and look for butterflies, bees, moths, and flies on the flowers of familiar trees such as black cherry, dogwood, and magnolia. Peek in neighborhood yards to observe azaleas, milkweed, and those beautiful little violets that pop up seemingly out of nowhere. In vegetable gardens, watch bees and other insects provide free gardening services as they pollinate squash, melons, tomatoes, and beans. Take a stroll along Sligo or Rock Creek parks and watch what happens when Spring Beauty, Jack-in-the-Pulpit, and others are in bloom. You don’t need to know the names of any of these plants or their pollinators to just enjoy the show.

What is Pollination?

Pollination is central to successful reproduction in most plants. It is the transfer of pollen grains from the anthers of one flower to the stigmas of the same or another flower. Movement of pollen via wind is a common strategy and in our region we helplessly encounter this each spring as large quantities of oak and pine pollen move through the air in the hopes that some of it will land on flowers of the same species. Although rare, water can act as a medium for pollination. But worldwide, more than 70% of flowering plants rely on animals to transport pollen for them.

The relationships between flowering plants and their pollinators have been evolving since the early Cretaceous (140 million years ago). These are mutually beneficial relationships in which the animal gains food and nutrients, and the plant is assisted in reproduction. The plants produce nectar, a nutritious sugar-based substance that attracts the pollinator, and the pollen is picked up in the process of collecting the nectar. There are species that cheat of course, and have become adept at “nectar robbing,” by taking nectar without passing the anthers of the flower where pollen is located. It’s fun to watch a mixed group of bee species on flower garden plants such as Hasta to see which of them enter through the mouth of the flower and which ones make but a brief stop at the base of the flower, where a tiny hole divulges their more direct route to the nectar.

Flowers use color, shape, odor, and timing to appeal to pollinators. “Pollinator Syndromes” describe flower characteristics, or traits, that may appeal to a particular type of pollinator. Plants such as the Maryland state flower, the Black Eyed Susan, provide easy access to nectar and attract a variety of pollinators. Others such as the Trumpet Vine have evolved to minimize the amount of pollen wasted by random visits of pollinators to other flower species. With its bright red flowers and deep tubular blossoms it specializes in attracting hummingbirds which can reach the nectar with their long straight bill. If you encounter Skunk Cabbage in bloom in early spring along local creeks you may be put off by the skunk-like odor, but it is a siren call to beetles and flies.

Who are the Pollinators?

Pollinators come in all shapes and sizes. At least 200,000 invertebrate species act as pollinators including bees, butterflies, moths, flies, beetles, and yes, even mosquitoes. (While the female mosquito is extracting blood to produce eggs, the males are extracting nectar.) There are an estimated 2,000 species of vertebrate pollinators. Hummingbirds and bats of course, but also surprises like doves, opossums, and lizards.

Pollinators provide indispensable ecological and economic benefits. Several species do both. The Mexican long nose bats pollinate both the saguaro cactus, which provides homes and food for a multitude of desert species, and the Agave, which supplies us with tequila for our margaritas. Globally, pollinators are important for the production of roughly 30 percent of the human diet, edible oils, fibers such as cotton and flax, alcoholic beverages, and medicines created from plants. In the US more than 150 food crops like almonds, apples, blueberries, tomatoes, and squash rely on pollinators. A lot of our favorite imports – like chocolate and coffee – too.

Insects are the dominate pollinators world wide, and bees are considered the most important. There are over 4000 species of bees in the US, and with a few exceptions they are wild bees native to the US. But despite this, when people hear “bee” most think of the honeybee. Honeybees were brought here from Europe in the seventeenth century as a crop pollinator and they have become the single most economically important pollinator in the US. Several estimates of the yearly agricultural services provided by pollinators exceed $15 billion. Pollination services provided by wild bees are also important and have been estimated at $3 billion per year.

Pollinators in Danger

In 2006, the National Research Council put out a report, Status of Pollinators in North America, which documents a serious decline in native pollinators. The report identifies the main causes as habitat loss, pesticide use, and diseases. Habitat destruction is caused by changes in land use. When people convert wild lands for domestic uses the food and nesting requirements of many pollinators are disrupted. Pesticides are a major threat to insect pollinators, although precautions such as better regulation, avoidance of overspray, and changes in the type and timing of pesticide use can reduce the threat.

The US Fish and Wildlife Service lists over 50 pollinator species as threatened or endangered. Continued declines in pollinator activity could mean rising costs for pollinator-dependent fruits and vegetables and the disruption of entire ecological systems.

There are some encouraging responses such as the creation of new habitats in some unlikely places: the US Golf Association’s Wildlinks Program is creating wildlife habitat along golf courses; the Farm Bill provides incentives for farmers to build permanent vegetative buffers next to agricultural fields; and PEPCO has been preserving open sunny pollinator friendly habitats along its transmission line corridors such as east of New Hampshire Avenue in lower Sligo Creek Park.

Honeybees and Colony Collapse Disorder

Honeybees have been in the news the last several years because of concerns about what is being called Colony Collapse Disorder (CCD). CCD results in adult bees abandoning their hives, while leaving the young, the queen, and the honey behind. Since the syndrome was identified in 2006 beekeepers are reporting losses of over 30 percent of their hives annually. Significant research has been conducted to understand CCD but as of yet no clear cause has been identified. Most researchers believe CDD is caused by a combination of factors including but not limited to pesticides, parasites, and stress from apiary management such as overcrowding and long distance movement of colonies for crop pollination.

What You Can Do To Protect Pollinators

There a number of steps you can take to protect and encourage pollinators.

  • Create your own pollinator-friendly garden using a wide variety of native flowering plants. Encourage the planting of native flowers in open spaces and outside public buildings.
  • Reduce the level of pesticides used in and around your home.
  • Encourage local clubs or school groups to build artificial habitats such as butterfly gardens, bee boards, and bee boxes.
  • Support agriculture enterprises with pollinator friendly practices such as farms that avoid or minimize pesticide use.
  • Encourage government agencies to take into account the full economic benefits of wild pollinators when formulating policies for agriculture and other land uses. Stress the need to develop techniques for cultivating native pollinator species for crop pollination.
  • Bring the importance of biological diversity to the attention of your state and national representatives. Stress that diversity includes beneficial native insects. Be prepared to provide local or regional examples of important species.
  • Support funding for research on pollinators and the economic benefits they provide.
  • Educate your friends and community about the importance of pollinators.

What You Can Do To Protect Pollinators Fact Sheet

Creating Pollinator Friendly Gardens

Pollination occurs in habitats that support and provide for both the pollinator and the plants that they pollinate. Any piece of land from a small urban backyard to large tracks of wilderness can contribute to the mosaic of habitats. Whatever the area of land under your care, there are several easy things you can do to help protect pollinators and sustain pollination services.

One of the easiest (and most rewarding) ways to provide suitable habitat for pollinators is to plant a wide variety of locally native flowering plants in your garden. Beyond your own backyard, you’ll find many other places where pollinator habitats can be restored or protected. Through community or school gardening programs, you can encourage the planting of native flowers in local spaces such as parks, playgrounds, roadways, golf courses, and around public buildings. Vegetable gardens are another great way to provide food for both you and native pollinators.

National Pollinator Week

Each year the final week of June is celebrated as “National Pollinator Week” with a variety of events across the US. In September 2006 the US Senate signed Resolution 580 designating National Pollinator Week to recognize “the importance of pollinators to ecosystem health and agriculture in the United States”. The Secretary of Agriculture followed with a proclamation “calling on the people of the United States to join in celebrating the vital significance of pollinators”. www.fws.gov/pollinators/pdfs/pollinatorweekres580.pdf

For more information and a list of other events across the country visit Pollinator Partnership.