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Any Boat in a Storm…Unless It’s a Raft of Fire Ants

by Liz Clift

Have you seen the photos—and worse, the video!—of the giant mats of floating fire ants (Solenopsis invicta)  in the wake of the flooding in southeast Texas? Yeah, us too, and we’ll admit they’re a bit horrifying.

But, they’re also fascinating.

Fire ants are invasive to the US and they love floods. Or, at least, they evolved to survive floods on river banks in South America, which means they happily use flood waters to relocate, which perfectly explains why my grandparents who lived in southeast Texas never actually removed them from their yards by spraying them with the water hose. When the waters rise, fire ants form “rafts” of thousands or millions of fire ants using their mandibles and their sticky feet and can do this in under two minutes. From there, they switch out the submerged ants with those that are drier, which helps keep the colony afloat.

In this configuration, they’re able to drift around on the flood waters until they reach a tree, land, or other suitable dry area (aka, literally anything solid) that they can scramble up.

Sure, you might be thinking, but they can probably be disturbed the swirling a stick through them, right?

Guess again.

If their configuration is disturbed, they will reconfigure to fill the hole (and I don’t know about you, but I wouldn’t want any of those little biters to come at me via a stick I was just using to torment them, especially because during flood times they are apparently more aggressive and more venomous. (More on that fun fact in a bit).

So what works?

Apparently dish soap, which will cause the configurations to break up and the ants to drown because they aren’t able to trap air near their bodies.


These fire ant rafts, fortunately, can’t last forever.

Post-Katrina, fire ant populations in New Orleans and other impacted areas decreased because it took weeks to pump all of the flood waters out. Those populations have never rebounded.

Which, many SE Texans might see as a good thing, especially if they’ve stepped in a fire ant pile before. Unlike regular ants, which will bite and then spray an acid (isn’t nature fun?) fire ants like to bite, hold on, and inject a poison into you that has 46 different proteins. Some people (somewhere slightly above 1:100 people) are pretty susceptible to this and can experience an allergic reaction or hallucinations. The rest of us just get welts (after Katrina, people were apparently entering field hospitals with welts upon welts from fire ants, after wading through the waters). But remember how I mentioned that right now they are more venomous? It averages 87% more venom per bite per ant. Yeah, that’s just making everything about this more of a nightmare.

How the floods from Harvey will affect fire ant populations in SE Texas remains to be seen, and will be largely determined by how long it takes the flood waters to recede (or, you know, a bunch of folks going out with bottles of Dawn to combat the terror mats the ants have formed).

A reduced population could be a good thing for more than just humans though. Ground nesting birds (like quail and meadowlarks) as well as some reptiles are also impacted by fire ants (whatever you’re imagining, that’s probably right) as well as native ant species, which are usually out-competed in areas cohabited with fire ants.

Who else wouldn’t be sad to see fewer fire ants? Ticks. Fire ants love to eat ticks.

So, if you’re searching for a bright side, wherever these fire ants wind up will likely be very free of ticks for the foreseeable future.

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Denver’s High Line Canal: A History of Irrigation & Recreation

By Liz Clift

One of the easiest ways to get water from one place to the next is to let gravity do the work. While on the extreme end, this creates waterfalls, if the change in elevation is more gradual, it can create a meandering waterway. This is also the principle behind high line canals. The canals are constructed on the high line of elevation, and often meander to simultaneously follow the higher points of elevation while incurring only a small change in elevation over the course of a mile.

Construction on Denver’s High Line Canal (HLC) was originally completed in 1883, a mere 24 years after the gold rush that sparked white settlement in the Cherry Creek and South Platte River area. The original canal covered 71 miles, in what is now Douglas, Arapahoe, Denver, and Adams counties, and irrigated 20,000 acres. The canal loses about two feet of elevation for every mile it covers. Denver Water took over the canal in 1924, and maintains management of the canal.

Now, the canal covers 66 miles. Alongside most of the canal is a popular recreation trail. Although some areas of the canal are currently inaccessible to the public, the High Line Canal Conservancy is working with Denver Water and others to improve connectivity along the entire trail while preserving the natural character of the trail. Part of the vision planning, according to the High Line Canal Conservancy website, includes development work that is aimed toward increasing the amount of water the canal can hold and convey. The canal was designed to convey 750,000 million gallons of water a day, but currently only moves about 71 million gallons. There are multiple factors weighing into this lower-than-planned conveyance, loss to seepage and evaporation.

High Line Canal Trail, Photo by Chris Loftus

In fact, the canal is often dry. This is because Denver Water operates the canal only intermittently, to deliver water to the last remaining HLC customer, and to nourish trees that thrive on more water than is typical for this arid region.

There are plans to further develop and manage the HLC, including developing continuous trail connectivity* and temporarily detaining higher flows a bit longer through segmenting berms, which will provide some water quality improvements. This change may also alter the ecology of the canal slightly by shifting which soils are wet longer, although these higher flows are not expected to be a regular event. Vegetation that could be supported includes cottonwood (Populus deltoides), which provide broad and dappled shade to the canal, the adjacent recreational trail, and human and non-human (such as deer and foxes, as well as aquatic animals like crayfish!) users of the trail and the canal, as well as native shrubs like snowberry (Symphoricarpos albus) and willow (Salix spp.) which provide shelter and forage for many species of bird.

High Line Canal, Photo by Chris Loftus

The canal also provides a nesting spot for turtles. A friend of mine was recently walking along the HLC, and came across a young painted turtle (Chrysemys picta). This is where I fully disclose that I love turtles, and seeing her picture on Facebook of the baby painted turtle made me want to immediately hop on my bike and start cruising along the trail in hopes of finding one also.

Painted turtles thrive in habitats with slow moving waters and soft bottoms with ample basking spots (such as partially submerged branches), which pretty much describes the HLC, when it has water, perfectly. They consume aquatic vegetation, small fish, insects, and crustaceans.  As a child, I caught baby painted turtles with a net. They would often be basking on top of pockets of algae, their hind legs stuck straight out behind them, as though they were flying. I loved noticing the differences in their plastrons which range from pale yellow to red with dark markings in the middle. I loved that if the baby turtle was especially young and its shell hadn’t begun to harden, that I could feel its heart beating on my palm.

Juvenile painted turtle, photo by Liz Clift

The increased connectivity proposed for HLC could provide more access for those who live along, or near, HLC—or have access to it from other Denver-area trails that intersect it—the chance to experience more of the biodiversity along the canal. Although in this post, I only talk about a couple of plant species, and turtles, the canal is an important migration corridor for a variety of animals, and also hosts many different plant species.

In addition, increased connectivity of the trail could increase beneficial health outcomes for those who access the trail. Daily physical activity, including biking, walking, and horseback riding (all of which are activities people engage in on portions of the trail) is linked to physical health benefits, as is general contact with green space, which more studies are indicating benefit our overall well-being. In The Nature Principle, Richard Louv writes, “In wilderness, and in natural cases or even natural urban parks, we find our senses….” He puts forward the idea that being in nature, and being present in nature (rather than still engaging in technology) helps nourish our deeper senses, and the very essence of our human intelligence.

Updates on the progress of the HLC can be found through the City & County of Denver and the High Line Canal Conservancy websites.

*The City & County of Denver has made conceptual designs of some of this increased connectivity available through public meetings and its website.


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Something Fishy This Way Comes

By Liz Clift

One of the definitions of ecology is the study of how organisms relate to one another and their environment. Think back to your childhood classrooms when you considered food chains. For the most part, they were structurally pretty simple.

Simple food chain, created by: Great Ecology

Slightly more complex are food webs, which showed interrelated dietary preferences. Animals with diversified sources of food are generally seen as better able to tolerate disruptions to the food web. For instance, a grizzly bear (Ursus arctos ssp.) eats salmon (Oncorhynchus sp.) in the food chain above. But as this is expanded into a food web, we also see that grizzlies eat berries, roots and tubers, small rodents, and even carrion or human food when it’s available.

Simple food web, created by: Great Ecology

If diet alone determines a grizzly bear’s survival, and say, chinook salmon (Oncorhynchus tshawytscha), are eliminated from the food web due to changes in how a river flows (perhaps because of a dam), the grizzly would, theoretically, simply rely more on other sources of food. Case closed, right?

An ecologist—by training or by curiosity about the world—knows it isn’t this simple.

If that same river is dammed, the grizzly might be able to find other sources of food, and do well enough, but the health of the river is impacted, as is the health of other apex predators, like orcas (Orcinus orca). Some orcas have diversified diets and will also prey on seals and other marine mammals or fish and so would feel less impact from the extinction of salmon species.

However, according to an article from American Rivers, published in June of this year, a distinct population of fish-eating orcas, called the Southern Resident Killer Whales (SRKW) waits for a salmon feast at the mouth of the Columbia River each spring. Although SRKW mostly eats chinook (Oncorhynchus tshawytscha, which make up 80% of their diet), they will also eat other salmon—and each whale eats 18-25 of these 30+ pound salmon every day. For that population to remain at its current level, they need at least a half million salmon a year—and if we want them to reach their recovery level (140 individuals), they would need a million salmon a year. It should be noted that since this group of orcas was first counted in 1974, the population has not been higher than 98 individuals (1995). This population lives in the Salish Sea, and Granny (J2), the oldest living whale until her presumed death in 2016, used to be part of their population.

L79 of the SRKW, in Puget Sound. Image from: Wikimedia Commons

SRKWs rely on salmon populations, and although they will travel through the Salish Sea, and down through the Haro Strait and Strait of Juan de Fuca, and are often spotted near the San Juan Islands, salmon populations in these areas are decreasing—and have been for a long time.

Unfortunately, structures we use for hydroelectric power or river control (like dams) can impede fish passage, and by extension, fish reproduction. Overfishing, algal blooms, non-point source pollution, and the disconnection of floodplains can all also impact river health, and by extension the ability to reproduce and the health of fish who use these rivers. (See our blog on healthy and connected floodplains!)

To give you an understanding of how these things have impacted salmon populations, more than 800,000 salmon used to return to the Yakima River every year to spawn. However, increases in agriculture and large reservoirs that were built without fish passage systems have impeded this population. In 1990, only 3,000 to 4,000 salmon returned to this river system each year. A variety of groups, including government agencies, tribal entities, recreation groups, non-governmental organizations, and others have been working to restore salmon populations. This includes reconnecting floodplains, and restoring instream habitat, as well the establishment of local hatcheries where supplemental stock is raised.

These are important steps to restoring salmon populations, as are dam removal projects, like the Elwha River Restoration Project. This is the largest dam removal in US history, and now the river is thriving—tons of sediment have been pushed out, salmon and steelhead are running the river, small squid are making their homes within the estuaries, and other animals including elk and shorebirds, appear to be thriving in the regenerating ecosystems (including young forests) that are moving into former reservoir areas.

The role of salmon in riverine ecosystems isn’t just limited to their benefits to bears and orcas though. They play an important cultural role for many Native peoples, a large economic role for people in the Northwest, and act as “pumps” that move ocean nutrients into lower productivity rivers. In fact, salmon can support the growth of forests as their remains are dispersed by predators, which in turn, provides more shading of the rivers, increased bank stabilization, and improved water quality before it ever hits the river (among other ecosystem services). In fact, salmon populations in Alaska contribute up to 25% of nitrogen in foliage!


Restoring and protecting salmon habitat—and salmon themselves—is critical because so much evidence points to wild pacific salmon as a keystone species for the northern Pacific. So, as you think about those food webs you once worked on, think about all the lines you might need to erase if salmon were to disappear.

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Healthy & Connected Floodplains

By Liz Clift

What does it mean to have a connected and healthy floodplain?

First, let’s start with what floodplain even means. It’s the relatively flat land adjacent to a river or stream that is inundated with water during high flow events, which most of us simply call floods. As a result of this flooding, the land is generally highly fertile and biodiverse, and marks a transition zone between the river and the upland systems.

If a floodplain that has been disconnected is often characterized by steep, high, or concrete banks that cause the water to move through more quickly. This can add pressures to manmade water control systems, such as dams or levees and reduces water quality benefits.

A connected and healthy floodplain, on the other hand provides riverine systems more room as they rise, and improve water quality. As the water overtops the banks of the river, floodplains allow sediment and nutrients to settle out, and provide an opportunity for additional water to seep into underground aquifers, which is a primary water and irrigation source for many communities around the world. In addition, connected and healthy floodplains provide habitat for a variety of plant and animals species.

Parana River (Argentina) floodplains. Image from: Wikimedia Commons

But that’s not all: floodplains also provide fertile grounds for agriculture, due to centuries of nutrient deposits. Depending on the current course of the river system, these nutrient rich areas may or may not be within 100-year or 500-year floodplains, and this is something landowners may want to consider as they consider development options, crops, and systems to alleviate the pressure of periodic flooding.

There are, of course, more benefits to connected and healthy floodplains, which is part of why river restoration often includes examining floodplain connectivity and working to improve or restore floodplain connectivity as part of the restoration plan. Depending on the needs of the community, this restoration work can take many forms, including:

  • Breaching or removing levees to allow floodwaters to reach the floodplains;
  • Installing flood bypasses that allow for controlled flooding (such as weirs or floodgates);
  • Excavating a floodplain terrace, which helps offset the vertical difference between the flow levels and the floodplain;
  • Setback levees, which allows more water to reach floodplains while still providing flood protection to areas behind the cities;
  • Adding sinuosity back into channelized streams and culverts;
  • Countour and keyline ploughing to direct higher flows into floodplains; and
  • Addressing flow regulation to restore minimum floodplain activating flows.

Restoring floodplain connectivity benefits humans as well as plants and animals, and the fact that floodplain restoration has become an integral part of many river restoration projects is a reason for hope about how the impacts of flooding may look different in the future.

Great Ecology has worked on floodplain restoration projects in several states, across dozens of projects.

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Spotlight on Datura: A Poison Plant

By: Liz Clift

This is the time of year when, in the evenings, I can find bees buried into the trumpeted blossoms of Datura sp. These plants are commonly called datura, as well as devil’s trumpets, moonflowers, and jimsonweed (among other names). Datura is part of the nightshade family (Solanaceae) and all species of datura are poisonous, especially the seeds and flowers.

In my neighborhood, there are a few isolated patches of well-established datura spills onto the sidewalks in the summer. It is here I go looking for bees in datura. The bees crowd into the Datura blossoms—sometimes as many as six or seven at a time! —which open as the day cools into night. Fortunately for us, and for the local honeybee keepers, there’s no evidence that honey that may have been partially created from datura flowers has had any ill effects on people.

Datura. Image from: Wikimedia Commons

As a child, in the south, I would sometimes go on early morning walks. Datura, in bloom, and reflecting the light of the moon, appears exceptionally bright and I would marvel at this plant that defied what I considered at the time to be a basic premise of being a flowering plant: flower during the day so you can be pollinated. At the time, I didn’t know there were nighttime pollinators.

Large moths, including hawkmoths, are among other pollinators of datura, although I haven’t observed these pollinating the blossoms of my local plants (I also haven’t gone looking for them). Hawkmoths have been observed nestling their bodies inside the blossoms, and staying for a while, rather than hovering while collecting nectar. This may allow more pollen to accumulate on their wings, and thus increase the rate of pollination for this plant.

Perhaps you’re wondering why anyone would plant this plant, knowing it’s poisonous. Although people have a variety of reasons, I imagine that its large, showy blossoms are one reason.

Datura Blossoms. Image from: Wikimedia Commons

It’s good to be wary of datura, like other poisonous plants, as consumption can lead to death. However, many of these plants that we fear have long traditions of being used by our ancestors. It’s important we understand how these plants have been used historically. As with everything, the dose makes the poison (and in some cases, that is incredibly small). In this case, the specific species of datura, along with the dose can make the poison. The ethnobotany of daturas includes:

  • Painkiller (Aztecs);
  • Ritual zombificiation (Caribbean peoples);
  • Creation mythology (Chumash peoples);
  • Sacred visions (various peoples); and
  • Treatment of bruises and broken bones, as a poultice (various peoples).

Datura, along with other poison plants may also be a key component of our folklore that witches ride on brooms. But I’ll let you google that yourself.

Datura seedpod. Image from: Wikimedia Commons

Although datura is a poison plant, and perhaps you’re feeling some healthy wariness about it, it’s also important to remember that other animals may rely on it, and that it has co-evolved with certain pollinators to provide a food source at a time of day when fewer food sources are available.

If you’re curious if it’s growing near you, take a walk this evening, or tonight, or tomorrow morning and take a look. Its large blossoms are distinctive, and it’s a good way to get an appreciation of what other things flower in your region during these hours. Plus, since it’s National Pollinator Week, you’ll have the opportunity to go seek out the pollinators that live in your community.

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Soil as Iowa’s Heart of Agriculture

By Liz Clift

Iowa became part of the heart of American agriculture, due to the rich—and thick—topsoil it contained as white settlers moved across the plains. Iowa’s nutrient-dense is, in part, due to Iowa’s placement between the Missouri and the Mississippi Rivers, which form the majority of the eastern and western borders of the state. The floodplains from these rivers built up stores of nutrients, as did the history of large grazing herbivores that would have once dominated the plains, including bison, elk, deer, and even mastodons.

Unfortunately, that topsoil is disappearing. In the 1850s, Iowa had 14-16 inches of top soil; as of 2011, it had about half that. In 2014, parts of Iowa lost 15 million tons of topsoil due to erosion caused by storms.  The remaining soil is being stripped of nutrients, due to monocropping, which over time, depletes certain nutrients from the soil. Even when fields are left fallow or with a cover crop for a season or two, the nutrients are not necessarily returned to the soil.

There’s a joke I heard shortly after I moved to Iowa in the mid-aughts:

Person 1: Have you seen the four views of Iowa?

Person 2: The four views of Iowa?

Person 1: Yeah. Corn on the left, [soy] beans on the right. Beans on the left, corn on the right. Beans on the left, beans on the right. Corn on the left, corn on the right.

During the growing season, that’s pretty much true.

And it means that most people don’t understand how much natural beauty Iowa once had—and still has. The prairie plants that historically grew in the area are notable for their long root systems. These root systems not only helped stabilize the soil and retain moisture (or get to moisture during drought years)—the roots also helped prevent soil compaction and drew nutrients further beneath the surface of the soil toward the top, making these nutrients more available for plants with shallower root systems, and younger plants.

Prairie Roots. Source: Wikimedia Commons.

There are only isolated prairies now, many restored, some historic. Some farmers are moving toward more sustainable, or even regenerative, agricultural practices. If you’re driving or biking across Iowa’s rolling hills, you might find yourself admiring a polyculture farm that includes nut trees, fruit-berry bushes, and row crops, with ducks or chickens roaming about. You might find yourself alongside someone’s land that’s been put into the Conservation Reserve Program (CRP), which has historically paid farmers to remove land from agricultural production and plant species that will improve functionality.

Herbert Hoover National Historic Site, in Iowa. Source: NPS.

Of course, in Iowa (and elsewhere), there is a lot of focus on what agricultural practitioners—which I’ll classify as everyone from conventional farmers through prairie restorationists—are getting wrong (or right). Who is getting what wrong or right, in many cases, appears to be dependent on what, specifically, any individual’s priorities are.

As we think about what’s going right or wrong, we must also remember that we have made major changes to the way the Midwest looks—including the use of agricultural tiles that effectively keep the land from becoming swampy, the removal or extinction of large herbivores, controlling of fires, the decimation of native plant species, and channelizing streams and rivers. Some of these things are more easily remedied than others.

Loess Hills, at Iowa Prairie Conference. Photo Credit: Liz Clift

Great Ecology is working to reconnect an Iowa stream with its floodplain, which will include some native prairie restoration. There are prairie management activities, which may include prairie burns, meant to replicate some of the more natural processes that enable tallgrass prairies to survive. A prairie conference occurs each year in the Loess Hills (this year is focused on restoration, reconstruction, and protection). Certain agricultural practices, including CRP, facilitate the rebuilding of the soil and its nutrients. Some individuals are transitioning bluegrass lawns into native grasses.

And these are just a handful of the activities that could work, or are working, to maintain or improve soil health.


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Hands On Erosion

By Liz Clift

Editor’s Note: This post provides a hands-on experiment you can do with children to help them understand how erosion and floodplains work to re-distribute nutrients, especially in flood events. You may want to couple this with reading news reports about floods (new or old) for older children, or with a visit to a local brook, creek, stream, or river to try and identify high (or low) water indicators, such as damage to trees, bank erosion, detritus or debris from previous floods, or to observe how or if the bank has been stabilized through placement of riprap or vegetation.

Years ago, I lived near a pond. During heavy rains, it overtopped its banks, crept toward the nearby playground, and over a walking trail. It would back up into its inlet, which was lined with riprap and willows. During these rains, it seemed impossible that when the waters receded the fish and other animals that lived in the pond would retreat as the water dropped.

But of course, for the most part, the fish, turtles, crustaceans, and other animals retreated as the water levels returned to normal. The flood waters would leave detritus—dead grass, small animals tangled up in the summer clots of algae that snagged on the blue grass that surrounded most of the pond, decomposing leaves—and nutrient-rich muck. No one ever did anything about the detritus. Sometimes geese or ducks would pick at it, but for the most part, it decomposed along the upper banks of the pond.

This is similar to what happens when other bodies of waters, such as rivers, flood—and part of what has made flood plains historically beneficial places for agriculture. The flood waters deposit nutrient-dense material onto the flood plains, and over time, these materials build up.

Modified fluvial plain, from a Prentice Hall image by an unknown artist

You can replicate this for children in your life several different ways. One way is with andwich cookies and a milk (not chocolate) of your choice. You’ll need at least one sandwich cookie for each person who is participating in the experiment, a small cup of milk for each participant, and a shallow-bottomed bowl or a plate with fairly high edges for each participant.

Start out by placing the sandwich cookie(s) at the bottom of bowl on one side. Replicate erosion by slowly dribbling milk over the sandwich cookie and observing what happens. You might ask the children if they notice the milk turning colors. You might ask if they notice small crumbs from the sandwich cookie being carried away.

Ask the children to observe what happens as the sandwich cookies continue to soften. Does the erosion speed up or slow down? What happens if you add more milk?

They should see the sandwich cookie “eroding.” They should notice that the crumbs follow a particular pattern (the exact results will depend on the bowl or plate you’re using).

Ask the children to pour more milk in to represent a flood. How does this change the distribution of the crumbs? What happens to the sandwich cookie?

You can ask children to use a straw to gently suck up some of the milk (some crumbs will come too, and that’s okay). This will allow them to better see how the crumbs are distributed.

You can repeat the experiment using sandwich cookies that are pre-crumbled and see how that changes things.

You can also do this with other cookies, based on dietary needs or preferences. You might do it with some potting soil and water on a cookie sheet or in the garden. The goal is to help children engage in ecological processes, so that they can better understand not only what they see in the natural world—but so that they might grow to care about it.

You can also incorporate landscape architecture or engineering (does arranging the sandwich cookies or soil in a different way change what happens when you add milk/water? How can you slow erosion through design? Can you alter patterns of deposition?

Give it a try. Get dirty.

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2017 Waterfront Alliance Conference Round-Up

By Michael Kaminski

Last week Great Ecology staff boarded a yacht to attend the 2017 Waterfront Conference along New York City’s Hudson Riverfront. The annual event is hosted by the NYC-based non-profit Waterfront Alliance and features a variety of talks and panel discussions. This year’s topics ranged from how current national politics may impact our local waterways and waterfronts, measuring the success of mega projects aimed at restoring New York City’s degraded waterways and strengthening its coastlines, and even looking at whether investments in offshore wind energy benefit the health of the environment and harbor.

The day’s highlight was a speech by New York City’s Mayor Bill de Blasio, in which he regarded New York City’s 520 miles of coastline–longer than the coastlines of Miami, Boston, Los Angeles, and San Francisco combined–as one of the City’s most valuable assets. He acknowledged years of neglect and poor urban development policy that have led to large portions of the waterfront being inaccessible and cut off from the public. For decades, mayoral administrations have dreamed about a continuous and unbroken public greenbelt around the perimeter of Manhattan. In an effort to make this dream a reality, de Blasio reiterated his recent April 26 announcement that the City has pledged $100 million to revitalize a major stretch of Manhattan’s waterfront along the East River between 41st and 61st Streets.

To measure the quality of waterfront development, including future efforts stemming from the Mayor’s pledge, Waterfront Alliance developed Waterfront Edge Development Guidelines (WEDG), a tool to assess exemplary waterfront planning and design in the New York metropolitan area. WEDG, now in its second year, is doing for the waterfront what LEED has done for buildings; the program formalizes a set of best practices and a voluntary ratings system for waterfront projects that results in more access, better ecology, and increased resiliency amidst the growing threats posed by climate change.

Great Ecology has been providing guidance throughout the advancement of this cutting-edge tool by serving on the WEDG advisory committee. We look forward to watching the WEDG program grow as we all strive for a more resilient New York waterfront that provides valuable ecological habitat and access for all.

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Attracting Monarch Butterflies: Or, Which Milkweed is the Right Choice?

By: Liz Clift

Milkweed is sometimes considered a noxious weed, because its propagates readily – each seedpod contains hundreds of seeds. As such, it has been discouraged from growing on a variety of landscapes. However, monarch butterflies (Danaus plexippus) rely on milkweed (Asclepias spp.) to reproduce – milkweed is the sole source of food for their larvae (adults can sip nectar from a variety of wildflowers). In recent decades, there has been a lot of campaigning to encourage people to plant milkweed in an attempt to aid monarch recovery.

And based on acres occupied in the Mexican forest where monarchs overwinter, their numbers are on the rise. This past winter, they occupied 10 acres of forest, compared to their record low number of 1.66 acres in 2013.

However, monarchs still face problems, and one of those problems has to do with the type of milkweed people have been planting. Until fairly recently, the primary milkweed commercially available in the United States was tropical milkweed (Asclepias curassavica), which in warmer southern climates doesn’t die back during the winter.

Monarch Butterfly on Tropical Milkweed. Photo Credit: Tony Fischer Photography from Flickr Media Commons.

Since tropical milkweed doesn’t die off, some monarchs aren’t completing their migration, preferring instead to stay in the southern areas of some southern states, where tropical milkweed can bloom year-round.

So, some monarchs aren’t flying as far. No big deal, right?

If only that was the case.

Unfortunately, milkweed can also host a protozoan parasite Ophryocystis elektroscirrha (OE) which infects monarchs and queen butterflies (Danaus gilippus). The long and the short of it goes like this:

An adult monarch (or queen butterfly) carrying OE spores lays its eggs on a milkweed plant and in the process scatters those dormant spores on the eggs and the leaves of the milkweed plant. Larva consume their egg casing as they hatch, and may pick up OE that way, or through consuming the infected milkweed plant.

Once the dormant spores are in the monarch larva’s digestive tract, enzymes break the spores open and release the parasite. The parasites move into the intestinal walls and begin to reproduce asexually – and each OE parent cell can reproduce many times.

The majority of the damage to the butterfly happens during its time in the chrysalis. About three days before the adult emerges, OE spores begin to form and show up as dark patches that can be seen from the outside layer of the chrysalis. The infected adult butterfly may be too weak to emerge from the chrysalis, or to cling to the chrysalis while their wings fully expand. Those that survive are often smaller than healthy monarchs, and have shorter forewings, and they carry the spores on their abdomens. The cycle repeats.

OE also damages the outer layer of a monarch’s abdomen, which causes the butterflies to dry out and lose weight faster than normal. This is especially problematic for the butterflies when there are shortages of water or nectar.

The cyclical nature of this parasitic infection is exacerbated by the fact that when a milkweed plant doesn’t die off (or get regularly trimmed down) in the winter, OE can continue to survive on it. If a milkweed plant is killed off over the winter, the returning monarchs (at least those that are uninfected) have an improved chance of being able to produce eggs that will grow into healthy adults.

In recent years, more milkweed plants have become commercially available, and many organizations dedicated to saving the monarch provide resources for people to help them select milkweeds that are regionally appropriate and also appropriate for a particular set of growing conditions. This effort will, hopefully, curb OE infections in monarchs.

Swamp Milkweed (Asclepias incarnata). Photo from Tom Potterfield, Flickr Creative Commons.

Aside from planting regionally appropriate species of milkweed, how else can people help save the monarch?

There are also opportunities for citizen scientists to help collect data on infection rates in monarchs. Testing for OE spores is conducted by gently pressing a piece of clear tape to the abdomen of a monarch. The tape sample is then sent to a lab, where it is evaluated for spores (and total spore count) under light or electron microscopes.

This research helps scientists better understand not only what percentage of the monarch population is infected with OE, but how OE spreads through a population, or a region. This may lead to advances in how OE is treated—or how the message about the importance of planting native milkweed is spread.


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Native Wildflowers are Critical for Pollinators

By: Liz Clift

It’s National Wildflower Week—and from a restoration ecology perspective, it’s important to realize that wildflowers aren’t the same everywhere. If you decide to plant wildflowers in your yard, try to stay away from wildflower seed mixes, as these can contain varieties that aren’t native to your area (and may even be considered invasive!)

Instead, plant native wildflowers, which are adapted to the climate in your region, and which have co-evolved with native pollinators. The co-evolution aspect is important—especially for insect pollinators*, whose tongue lengths may be specifically adapted for particular types of flowers. A bee with a short tongue, for instance, can’t acquire what it needs from a flower with a longer corolla, such as Columbine (the state flower of Colorado).

It’s tempting to think then that a long tongue is better—or that just planting flowers with shorter corollas (yarrow, for instance) is better. But, long tongues are difficult to get into shorter flowers.

Bee tongue. Photo Credit: Ryan Abel through Flickr Media Commons.

And that’s not all. Some pollinators like a “platform” to land on, while others will hover or burrow into the flower. Some pollinators are more likely to be out midday, while others are crepuscular or even nocturnal. A variety of native wildflower species will help create preferred forage for a variety of pollinators—and will likely create a bloom pattern that lasts over several months, rather than peaking at one particular point and then leaving pollinators without additional sources of food.

In some cases, planting a non-native species of a plant (like milkweed, Asclepias spp.) can actually be detrimental. Milkweed is the exclusive host plant for monarch (Danaus plexippus) caterpillars – but depending on the type you plant, it may not die back enough to kill off the protozoan parasite Ophryocystis elektroschirrha (OE). OE, when ingested by monarch caterpillars, causes the adult butterfly to be much weaker than their healthy counterparts—and carry spores to spread to other milkweed plants.

This can result in a decline of monarchs.

Fortunately, there are many native species of milkweed you can plant, which are adapted for your region—though getting your hands on seeds for these varieties may be a little more difficult.

Swamp Milkweed (Asclepias incarnata). Photo from Tom Potterfield, Flickr Creative Commons.

If you’re not especially familiar with the native plants in your area—or have suddenly realized that your “wildflower mix” came from a company in the northeast and you live in Central California—there are a variety of resources that can help you focus your wildflower efforts to your region.

Many states have Native Plant Societies as well as university extension offices (like this one for Colorado and this one for Minnesota) that can help guide you toward an appropriate wildflower mix. The Xerces Society also provides lists of plant species by region. These easy-to-read lists note the bloom period (early, mid-late, etc.), common name, scientific name, flower color, maximum height, water needs, and additional notes that include what it attracts, shade tolerance, etc.

The National Wildlife Foundation has a Native Plant Finder (in beta) that allows you to search native plants by zip code and also spits out which butterfly and moth pollinators use particular plants as a host plant.

If you’re working on a restoration project, and are considering how to better include native pollinator habitat as part of your design, please contact us. Great Ecology has developed pollinator-focused plant palettes and landscape designs for a variety of projects, including one for a BASF site in New Jersey.

*There is also evidence that this makes a difference for other pollinators, including bats.

Prickly Poppy (Argemone polyanthemos), Bar Lake State Park, Colorado, October 4, 2014. From Wikimedia Commons.

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