host plants

Tropical Species Moving North | Earth Wise

April 19, 2021 By EarthWise Leave a Comment

Climate change is leading to warmer winter weather throughout the southern U.S., providing opportunities for many tropical plants and animals to move north. A new study by scientists at UC Berkeley looked at the changing distribution of tropical species driven by the warming climate.

Some species are appreciated in their new locations, such as sea turtles and the Florida manatee, which are gradually moving northward along the Atlantic Coast. Others, like the invasive Burmese python are not so welcome. That goes double for many insects, such as the mosquitoes that carry diseases like the West Nile virus, Zika, dengue, and yellow fever, as well as beetles that destroy native trees.

The transition zone, northward of which experiences freezes every winter, has always been a barrier to species native to more temperate places. For most organisms in such places, if they freeze, they die. Cold snaps like the recent one in Texas usually don’t happen for decades and are now likely to be less and less frequent. In the meantime, tropical species can get more and more of a foothold and maybe even develop populations that can tolerate more cold extremes in the future.

The warming climate is leading many plant species to expand their ranges, in some cases pushing out native species. The general story is that the species that do really well are the more generalist species whose host plants or food sources are quite varied or widely distributed and can tolerate a wide range of conditions. By definition, they tend to be the pest species.

We need to prepare for widespread shifts in the distribution of biodiversity as climate, including winter climate, changes.

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Tropical species are moving northward as winters warm

Photo, posted May 7, 2010, courtesy of Jim Reid / USFWS via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Non-Native Plants And Insect Decline | Earth Wise

January 15, 2021 By EarthWise Leave a Comment

Global insect populations have been in decline since the beginning of the 20th century. The decline accelerated during the 1950s and 1960s, and it has reached alarming levels during the past 20 years.

The causes of plummeting insect populations include habitat destruction, deforestation, climate change, light pollution, and the rise of industrial agriculture. This so-called insect apocalypse is being mirrored by a bird Armageddon because so many bird species depend on insects for their diets.

A still controversial, but increasingly likely factor in the decline of insect populations is the spread of non-native plants in agriculture, agroforestry, and horticulture. A recent study published in the journal Ecological Entomology presents recent data supporting the proposition that the widespread displacement of native plants is a key cause of insect declines.

Many insects depend on a limited number of plants for survival. In many cases, insects’ diets are restricted to a single plant family. When native host plants dwindle or disappear from an area, the population of insects that depend on those plants shrinks.

There are examples of insects that adopt introduced plants as food sources, such as silver-spotted skipper butterfly larvae feeding on invasive kudzu in the eastern U.S. But generally, the widespread incursion of non-native plants is harmful to native insect populations.

Non-native plants are especially popular for horticulture. Millions of acres of potential insect habitat have been transformed into food deserts for native insects. The authors of the recent study recommend that Americans should extensively include native plants in their yards to help preserve insect diversity.

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How Non-Native Plants Are Contributing to a Global Insect Decline

Photo, posted May 2, 2004, courtesy of Bernard Spragg via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Native Bees In A Honeybee World | Earth Wise

September 21, 2020 By EarthWise Leave a Comment

There is a great deal of attention on the plight of bees and other pollinators. Much of that focuses on the problems plaguing the large, domesticated honeybee colonies that are trucked from region to region to pollinate everything from almonds to fruit trees. Managed bee colonies have recently been losing more than 40% of their population over the course of a year. But overall, honeybees are still relatively safe. They are a globally distributed, domesticated species and are not remotely threatened with extinction.

But another group of bees – native bees – faces a different range of threats, most linked to habitat loss. Worldwide, roughly 20,000 native bee species have evolved over millions of years to thrive in countless habitats, where they have specialized in pollinating specific flowers and plants – in some cases just a single plant.

Scientists have estimated that, globally, 1 in 6 bee species is regionally extinct. In the United States there are about 4,000 native bee species, most of which are solitary bees that nest in the ground or cavities, with many that require just one or a few plant species for sustenance. At least 23 percent of U.S. native bees have declined, with bees in areas with heavy commodity-crop production particularly hard hit due to habitat loss and pesticide use. Other threats to native bees include climate-driven sea-level rise and increased temperatures, loss of host plants, and competition and disease from non-native honeybees. 50% of Midwestern native bee species disappeared from their historic ranges in the last 100 years. Four of our bumblebee species declined 96% in the last 20 years, and three species are believed to already be extinct.

Native bees are in big trouble.

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Backyard Battle: Helping Native Bees Thrive in a Honeybee World

Photo, posted December 2, 2017, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.