Invertebrates – Our Most Important Wildlife
By Denise Thornton
Many landowners want to encourage wildlife on their property, but perhaps the most overlooked and yet crucial types of wildlife are our insects and other invertebrates. They are essential to the food web, converting the energy of plants into food for fish, mammals, and birds.
“Mice, voles, and other small mammals have been called the hamburger of the prairie, but what are those mammals eating? Vegetation and seeds, yes, but also invertebrates. And nearly 90 percent of birdlife consumes invertebrates at some point.” says Micah Kloppenburg, Wisconsin Pollinator Habitat Specialist for The Xerces Society, a science-based conservation organization focusing on invertebrates.
Not only are invertebrates food sources for other animals, Detritivores, such as earthworms, millipedes, dung beetles, and others, are recycling nutrients for a new generation of plants in woodland, prairie, savanna or wetland by breaking down decayed matter and waste. “They are soil engineers,” Kloppenburg says, adding that “ants, beetles and others move soil detritus and reconstruct the soil and blend soil horizons.”
And consider the impact of pollinators (Kloppenburg’s focus), which contribute to one of every three bites of food we eat. “I like to add that farmers contribute to three of those three bites,” says Kloppenburg. “We really need to be sure that we are supporting both our farmers and our pollinators to sustain a healthy food system for humans.”
There are insects who are finding the landscape humans are altering beneficial, but they are not offsetting the decline of insect biomass and the decline and potential extinction of invertebrate species. As essential as invertebrates are, we are rapidly losing insect biomass. “If we take all insect life and weigh it on a scale, every year we are losing two percent of that insect biomass,” Kloppenburg says. Why?
1. Loss of Habitat: Ecosystems that support wildlife are a complex of food webs and nesting requirements. Human urban and agricultural development is compromising the systems that wildlife depends on.
2. Fragmentation of Habitat: As a particular habitat becomes more isolated, the genetic diversity that helps an individual species adapt to change may be lost. Also, in small, isolated areas, the range that an individual invertebrate may require may not be enough to sustain its life.
3. Changes in Plant Communities as a result of our human footprint: Invertebrates are contending with habitats significantly modified by agriculture and development, and invasive species have dramatically changed the structure of prairies, woodlands, and wetlands. Many plants that insects require for forage or nesting are on their way out. For example, about 500 invertebrates in Wisconsin are found only in prairies because of specific plants that they rely on to complete their life cycle. With prairies now at less than one percent of their original extent, we are seeing a decline in species that call prairies home.
4. Spray Drift: The industrial food system and many farms are reliant on pesticides, herbicides, and fungicides — any of which, even in minute doses may kill or reduce the fitness of an insect. Even if it is not the intended target, an exposed invertebrate may not be able to complete its life cycle and reproduce. “And there are secondary, inactive ingredients that are part of a formula that may be causing mortality as well,” says Kloppenburg. “When these compounds move into the water system, the wealth of invertebrate life in our riparian systems is affected.”
5. Climate Change: Along with shifts in preferred precipitation patterns and temperature tolerances for insects, changes in climate can disrupt the linkage between insect and plant life cycles. “Whether or not something is blooming at the appropriate time when a bee would normally emerge can have destructive consequences. “Maybe a leaf grew earlier than usual and has built up natural defenses because it is further along in its growth and can resist a tissue-feeding insect, or perhaps they don’t overlap at all,” Kloppenburg says.
How to Help
As the Xerces website says, insects are resilient, and conservation, restoration and management of habitat have been shown to produce positive outcomes for insect populations. All of us can do something.
Landowners can help by thinking about invertebrate habitat on their property. “It is the same for insects as for people,” says Kloppenburg. “We all require three key elements: 1. A nesting location, 2. Food and forage, and 3. Protection from damaging toxins.”
Invertebrates are looking for native species to complete their life cycle, because native plants are best for nesting and forage. “A lot of moths and butterflies form cocoons or chrysalises, and they require cover that our native plants provide to do that. Brambles in woodlands are good stem nesting locations for smaller bees. Dead wood is crucial to some species. “We talk about snags for redheaded woodpecker habitat, but it is equally important for bees,” Kloppenburg notes.
We think of prairies as where a lot of pollinators thrive. Prairie is in flower from early May to October, but woods provide spring ephemerals and trees provide early spring supplies of pollen and nectar. Maples and oaks don’t have showy flowers, but along with some native shrubs, they are an important pollen source for our earliest emerging native bee species. Douglas Tallamy, in his book, Bringing Nature Home, tell us that an oak tree supports over 500 different species of moths and butterflies – more than any other type of tree.
“Insect needs vary,” says Kloppenburg. “The different habitats support varying populations. On really hot days, like we have experienced recently, invertebrates are looking for shade and water just like the rest of us where they can rest and not overheat. Each habitat sustains an important part of the puzzle in the broader landscape. Whether it’s nesting or forage. Wetland, forest, and prairie each has a unique assemblage of native plants, and together they provide food sources and nesting locations. Many of our insects may find a food source in a prairie but may nest in a woodland. Its important to try and create a mixture of woodland and prairie with blooms that are available all through the growing season.”
“The Xerces Society has a fantastic website where landowners can learn more about management implications, pesticide reduction strategies, and find plant lists for particular locations,” says Kloppenburg. “Also look to local conservation organizations such as the Wild Ones, or your county or municipality conservation department.”
By Denise Thornton