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Falling Giants: The Death of American Trees

Falling Giants: The Death of American Trees, www.agirlinhergardne.com

Falling Giants: The Death of American Trees, www.agirlinhergardne.com

Last year I went to New York in October.

I live in the midwest so I have seen my share of Sugar Maples in fall, but I had never seen mountains of them. It was as if someone had lit the hillside on fire as the sun rose and set.

Now, imagine New England without its Sugar Maples. Gone, every one of them.

Soon you won’t have to imagine it. Soon you will have to imagine the mountains with the maples.

Forests without trees

The American chestnut (Castanea dentata) was the once the most common tree in eastern forests. No hardwood tree was more important to humans and wildlife. A single tree yearly made 6,000 nuts. These were prized by humans and animals for their vitamin C, protein and carbohydrates. Its wood was easily worked and also rot resistant.

In spring the chestnut’s blooms would turn the eastern forests into a winter wonderland.  There were so many trees that the forest canopy would look white. Pollinators loved this bloom, butterflies and bees alike.

To loose a tree like this would devastate a local habitat.  The entire food web would be effected, from the caterpillar all the way to the hawk. But it did happen, the chestnut was lost and 4 billion trees fell.

Cities without trees

In the 1930s it would be difficult to find a city street without an arching canopy of American Elms (Ulmus americana). These amazing shade trees stood like a vase as they grew high above the roadways. Forming an arch, the trees touched, creating a tunnel through which even the largest truck could pass.

From the east cost to the Great Plains these trees were used in cities and suburbs for street and backyard shade. But something was about to change the fate of 100 million trees.

The dangers of importation

I have never seen an American chestnut or an American Elm. Both tree species were decimated in my hometown before I was born. But why did they die?

The United States imports everything imaginable. Cars, phones, plants, bobble-head dolls and logs. These items come across the ocean on ships, in boxes on wooden pallets.

It’s the logs that killed the American Elm.

In 1931 a shipment of logs came from France to make furniture. It landed in a port in New York. But the shipment had more than just logs. It also had beetles. The European Elm Bark Beetle (Scolytus multistriatus) no larger than a pencil tip was the stowaway. This beetle has an advantage over the native American Elm Bark Beetles (Hylurgopinus rufipes). The European beetles come out in the spring, a month earlier than the native beetles. The European beetles also carried a stowaway. These beetles carried a fungus to which the American Elms had no immunity.

The fungus, Dutch Elm Disease (Ceratocystis ulmi), has been called the most significant event in the history of urban forestry. It changed the way cities look at trees.

Dutch Elm Disease changed the way cities look at trees. Click To Tweet

The American Chestnut also felt the effect of importation. During the late 1800s foreign chestnut trees were imported for the nursery trade and by 1904 the entire north-eastern United States was losing their trees. These foreign trees also brought a fungus, the Chestnut Blight (Cryphonectria parasitica).

Like the American Elm, the American Chestnut had no resistance to this new disease. The blight traveled quickly as spores, clinging to bird’s feathers, animals’ fur and insect’s feet until the once towering American Chestnut was reduced to small root sprouts struggling on the forest floor.

Changing urban forestry

The decline of the American Elm was a turning point for trees in cities. It showed scientists the power of a single invasive pest, altered laws and policies, created a new profession and increased public awareness of street trees. No longer were trees a passive decoration. They were falling around us.

It also found a way to repeat itself.

In an effort to lessen the loss of the American Elm, cities responded by looking for a replacement. They found one in the Green Ash (Fraxinus  pennsylvanica). Similar to the American Elm in shape and hardiness, this tree is now lining roadways like the Elm of the past, almost in exclusion of other types of trees. Within its growing range, the ash is at least 50% of the trees along roadways.

Ash Tree Cincinnati, Ohio 2016

Ash Tree Cincinnati, Ohio 2016

Then, in 2002, ash trees in Michigan started dying.

Scientists found a small green beetle beneath the bark of these dying trees. The Emerald Ash Borer (Agrilus planipennis) was a little known Asian beetle. How it got here is uncertain but it swept through Michigan forests. Unchecked by predators in this new land, the beetle was unstoppable and heading south.

It was a repetition of the American Elm disaster, only this time the beetle was going after more than one type of Ash tree. All species of ash were dying. As it spread, it began killing all ash trees in its path. Currently it is found in all states east of the Mississippi with Alabama and Missouri as the only holdouts felling 50 million trees. And it is creeping westward into Texas and Colorado.

The loss of the American Elm has been repeated with the Ash. Click To Tweet

As this is the second time street trees have been lost, we are able to see the impact it has on the cities and suburbs that depend on them. Areas that have been hit by the beetle are showing an increase in utility use. Electric useage in the summer has soared due to the loss of shade and water consumption has increased as residents try to water their unshaded grass.

In addition to an increase in utilities, property values have fallen as the trees die. Mature trees on a property have been shown to increase its value by $10,000. Add that to the cost of removal of a large tree at $500-1000 and homeowners are feeling the loss.

Stormwater districts are taking a hit also. The loss of large trees increases runoff during rains. Many cities sewer systems are out of date. Created in the early 1900s, they cannot handle current demands. The additional runoff due to tree death can flood these already overtaxed sewer systems and damage homes.

“The loss of large trees increases runoff during rains, flooding sewer systems and damaging homes.”

The American Forestry Association has attached a monetary value on a tree. A single tree is worth $73 in air conditioning, prevents $75 of erosion, reduces $50 of pollution and gives $75 of wildlife shelter. This totals, with interest, to a value of $57,151 for a 50 year old tree. And that is the value of a single tree. Now add in the loss of 4 billion American Chestnuts, 100 million American Elms and the 50 million lost Ash to understand the magnitude of the problem.

Loss of mast trees

The American Chestnut’s main wildlife value came from the nuts it produced. This annual nut crop is called mast. This term is used for any nuts, seeds, fruits or buds made by plants that are eaten by wildlife.

Many mast producing trees, like the oaks, have ‘mast years.’ This means that every few years they make a bumper crop of acorns. The American Chestnut was different. Every year was a mast year. Combine this with its tendency to flower well after the last frost meant that this tree was a reliable and needed food source for the forest food chain.

Nut producing trees can take years mature, sometimes decades. The Burr Oak produces its first acorn at 35 years! The American Chestnut was different, it could bear nuts at 5 years old. In addition to this, chestnuts were high energy food. They provided much needed protein, sugars and starches for wildlife in winter. And they were not bitter like acorns. In fact, they were so tasty that they were the primary fall food of deer, bear, turkey and squirrels.

American Chestnuts were important mast trees in the eastern forest. Click To Tweet

The loss of one eastern mast tree has had a lasting effect on the amount of wildlife an area can support, but losing a second could be even more profound. Unfortunately, we may see this occur sooner than later.

The Black Walnut (Juglans nigra) tree is considered a nuisance in the suburbs.  It tends to drop sticks and it’s messy walnuts onto rooftops and driveways. But for all its messiness, it is an amazing wildlife and timber tree.

Immature Walnut Fruit

Immature Walnut Fruit

Walnuts first bear at about 12 years old. They flower and fruit at the same time as the chestnut.  Unlike the chestnut, the walnut tree doesn’t make the same amount of fruit each year, it varies by how many nutrients the tree receives. These nuts are a favorite to all squirrels. In fact, it is almost difficult to beat the squirrels to the nuts. Beyond squirrels, mice, voles and some birds also eat this crop. The nuts are high in protein and essential fatty acids, which help these small animals survive winter. These small animals in turn are food for the predators of the food chain. The walnut is key in the food web.

Many insects live on a Black Walnut, one being the native Walnut Twig Beetle (Pityophthorus juglandis). This small insect is not found naturally on the Eastern Black Walnut but on Arizona Walnuts (J. major) which is a different tree. Black Walnuts are not native to the western states, but in the 1850s people began to plant them in the west. It is assumed, that due to this planting, the eastern Black Walnut first encountered the beetle.

In 2008, it was noted that Black Walnut trees in Colorado were dying. At first a drought was blamed, but as investigations continued the beetle was found. The culprit was partially the beetle, but definitely a fungus the beetle carried. Named Thousand Cankers Disease (Geosmithia morbida), it kills 100% of infected Black Walnut trees, but not the Arizona Walnut trees on which is lives.

“Thousand Cankers Disease kills 100% of infected Black Walnut Trees.”

This beetle usually stays in the western states, but it began moving eastward, bringing this fungus with it.  By 2012 it reached my home state of Ohio, where Black Walnuts comprise over half of the forested land. Ohio placed itself under quarantine.

The canker is now found in 9 western states and 7 eastern. Due to its mortality rate, things do not look good for the Black Walnut, nor for the wildlife that relies on its mast.

The University of Colorado made this sobering summary in 2010,“based on the patterns seen in the West, such a colonization [of the fungus] could very possibly develop into an uncontrollable outbreak. This might ultimately have the potential to destroy black walnut within its native range.”

Maybe the squirrels better bury some more walnuts this fall.

Saving trout

Great Smoky Mountains National Park is known for its sprawling mountains, scenic drives and trout fishing. Native to the Smokies, the brook trout and nonnative rainbow trout swim in 800 miles of the Park’s streams. Every year fishermen flock to catch them.

But did you know the trout are in danger?

In 1951 a small insect was found in Richmond, Virginia. It came from southern Japan and had an appetite for hemlock trees. It was the Hemlock Woolly Adelgid (Adelges tsugae). It was hungry and it was fast. It spread rapidly in the northern states, leaving stands of dead Eastern Hemlock (Tsuga canadensis) as marker of its passage.

Deep Shade under Hemlocks at Carver's Gap, Appalachian Mountains

Deep Shade under Hemlocks at Carver’s Gap, Appalachian Mountains

It also moved westward, ever closer to the Smoky Mountains. In 2002 it entered the park. Within the park it found a buffet of hemlocks. The largest and most common tree in the park. With over 90,000 acres of hemlock, some more than 500 years old, the Smokies were a small slice of insect heaven.

Killing large stands of this huge tree in just 4 years, the Hemlock Woolly Adelgid was making an impact. The Eastern Hemlock, also called the ‘redwood of the east’ is a critical species in the park. The Park Service started worrying.

The Eastern Hemlock creates deep shade, so much in fact that under its branches it is 2-4 degrees cooler than in the open. This is important for the streams that run under the hemlocks. The streams that house the trout. This cooling effect keeps the water temperature low which in turn increases the oxygen in the water and prevents algae from growing.

Hemlocks create the exact streams that allow trout to live. No hemlocks, no Smoky Mountain trout.

The shade helps the trout in another way. Rhododendrons are large shrubs that grow in the understory in the park. While they are native plants, sometimes they can grow a bit too much. Their growth chokes out smaller plants which decreases the diversity of plants at the ground level. The hemlock’s stop this with their shade. By shading the rhododendrons, hemlocks allow other plant species to grow on the forest floor, providing food for more insects. Trout love insects.

Dead Hemlock at Clingman's Dome, Smoky Mountains, 2014

Dead Hemlock at Clingman’s Dome, Smoky Mountains, 2014

And it’s not just Smoky Mountain National Park that is battling the Woolly Adelgid. It entered Shenandoah National Park in 1980 where it killed 80% of the hemlocks. The Woolly Adelgid is now found from Maine to Georgia and as far west as Kentucky and Tennessee.

 As the outbreak continues, the National Park Service is worried that “The impact of widespread loss of hemlock could trigger changes more significant as those that followed the demise of the American Chestnut.”

“The impact of widespread loss of hemlock could trigger changes more significant as those that followed the demise of the American Chestnut.”

Multiple species loss

So far it seemed that these tree deaths have affected just a single tree type, the ash, the hemlock, the walnut. But what would happen if more than one tree is lost? We may soon find out.

In 1996, a wooden pallet arrived from China. It was like all the others that come into New York ports, except this one had an extra passenger.  This passenger flew to a park in Brooklyn where it was found on some maple and horse chestnut trees. It was sent to a laboratory for identification. The identification came back as the Asian Longhorn Beetle (Anoplophora glabripennis).

The small black beetle with white polka-dots may look harmless. It’s almost comical in appearance, with antenna too large for its body. Unfortunately, this small bug is hungry.

It’s favorite food is any maple tree. An it has a lot to choose from. The United States has 12 native types of maple tree (Acer spp.), including New England’s fall favorite the Sugar Maple (A. saccharum).

But if it can’t find a maple, it doesn’t worry. See, the Asian Longhorn Beetle is not a 3 year old refusing his carrots. This beetle is not picky about what it eats. It will regularly munch on 9 different types of trees (see examples below, bold indicates a preferred host).

Asian Longhorn Beetle Host Trees
Maples (Acer spp.) Sugar, Silver, Norway, Red, Sycamore, Boxelder
Birch (Betula spp.) River, Yellow, Mountain Paper, Sweet, Dwarf, Paper, Swamp
Buckeye (Aesculus spp.) Ohio Buckeye, Red Buckeye, Horsechestnut
Elm (Ulmus spp.) American, Siberian, Chinese
Mountain Ash (Sorbus spp.) Mountain Ash
Willow (Salix spp.) Weeping, Pussy, White, Black
Ash (Fraxinus spp.) Green, White
Planetrees (Platanus spp.) American Sycamore, London Planetree
Mimosa (Albizia spp.) Mimosa
Poplar (Populus spp.) Eastern Cottonwood, Quaking Aspen, Black

As terrifying as this list is, it is not complete. There still is some question as to whether it eats any of the following: Hackberry (Celtis spp.), Rose-of-Sharon (Hibiscus spp.), Crab Apple (Malus spp.), Mulberry (Morus spp.), Cherry (Prunus spp.), Pear (Pyrus spp.), Oak (Quercus spp.), Locust (Robinia spp.) and Linden (Tilia spp.). That adds another 9 tree types to its menu.

The beetle isn’t so comical now. Its potential is staggering. The Purdue University entomologist Clifford Sadof offered this sobering statement, “It takes several years for it [the beetle] to get rolling, but once it gets rolling, it’s like a steamroller.”

“It takes several years for it [the beetle] to get rolling, but once it gets rolling, it’s like a steamroller.”

The ecological and financial effect of this beetle is scary. In New York, despite efforts for containment, the beetle has killed 20,000 trees. Imagine river banks eroding without birches or willows and Colorado’s mountain sides without the gold of Aspens. Hummingbirds will miss the Red Buckeye’s flowers, the wood duck will miss nesting in the American Sycamore. Imagine trees falling throughout neighborhoods and across streets. Imagine the increased runoff into our streams, clogging them with sediment, the summer sun baking rooftops. Imagine any Ash or Elm that has survived so far dying also.

Imagine a New England autumn without the sugar maple.

New York has tried to contain the beetle and in 2013 it was declared eradicated from Manhattan and Staten Island, but that victory was retracted in 2014 when the beetle was found in a Long Island backyard in an area not before infested.

Since its appearance, more than $236 million has been spent in New York alone battling the beetle in an attempt to prevent it from entering the forests of the state.

It just keeps popping up. The beetle found its way to New Jersey, who won the battle against it in 2013. In 1998 it was found in Queens, in 2002 in Central Park. Traveling in shipping containers the beetle found its way to Indiana in the 199os, it was quickly killed before it left the warehouse. It has appeared in Massachusetts and Chicago.

In June 2011 the beetle was found in Clermont County, Ohio poised to invade East Fork State Park. The state estimates that losing the battle with the beetle will cost 2.5 billion to the timber industry in maple trees alone and will endanger the jobs of 240,000 people.

Watching Yellowstone burn

During the beginning of the twentieth century forest fires were considered a destructive, unwelcomed event in the American wilderness. Because of this, the Forest Service began extinguishing all fires on public lands. But fire is a natural event, a much needed renewal. And by the late 1980s Yellowstone National Park needed that renewal.

The summer of 1988 became the worst fire season the park had ever seen. It was created by the perfect storm of conditions: accumulated downed trees, high winds, a summer drought and dry lightning. Most of the fires that season were started by lightning.

In an area with regular fires, dead trees are burned quickly and do not pile up on the forest floor. The fire isn’t hot enough to kill large trees, it merely singes the bark. But in this fire starved ecosystem, the fuel had been waiting decades. It burned hot, hotter than normal.

The resulting fire burned 36% of the park land, over 790,000 acres. The flames stood 200 feet high sending embers a mile ahead of the main blaze. It was so uncontrolled that it jumped across the Grand Canyon of the Yellowstone River. It endangered those in the park and the surrounding communities initiating evacuations and costing $120 million.

Luckily, the hot fire only killed deep roots in a small portion of the park. The rest of the land received a much needed cleansing. Even the Aspen, which were feared lost, came back stronger.

Fallen trees near Yellowstone Lake, 2016

Fallen trees near Yellowstone Lake, 2016

As of today, Yellowstone once again has an unusually large pile of dead trees waiting to burn. Trees killed by beetles. This summer I walked the trails around Yellowstone Lake and saw the sheer number of downed trees. Leaving the trail was not an option due to the tree fall.

Mountain Pine Beetles (Dendroctonus ponderosae) have always been a part of the western ecosystems. Their population has risen and fallen, their forces kept in check by the pine tree’s defenses and the coming of winter.

But then something started happening. The beetles started winning.

From Canada to Mexico, mountainsides began turning brown. Large swatches of pines are dying, trees that are important to humans and wildlife. It seems that no species of pine was spared. The Lodgepole Pine (Pinus contorta) was dying, as was the Jack Pine (P. banksiana), Limber Pine (P. flexilis), Whitebark Pine (P. albicalis), and the the spruces (Picea spp.) followed as well.

In some areas 100,000 trees can fall in a day. In Yellowstone, where the lodgepole pine is the most common tree, grizzly bears began struggling as pine seeds were not there to fatten them for the winter. In British Columbia the logging industry slump has impoverished towns. Campgrounds are closed due to falling trees. Soil is washing away.

University of Montana entomologist Diana Six has been studying the phenomenon and is troubled, stating “we need to see this [the mountain pine beetle] as a harbinger of what’s to come. We’re going to see one ecosystem after another begin to tip.”

“We need to see this [the mountain pine beetle] as a harbinger of what’s to come. We’re going to see one ecosystem after another begin to tip.”

Why are the beetles winning? It is a problem with more than one cause.

Due to human’s fear of forest fires, the beetle now has more food. As we put out natural fires, pine trees matured instead of burning. British Columbia alone has three times as many mature pines as it should. That’s three times more food than the beetles would have if the forests had burned.

Next the beetle has been enjoying our warmer temperatures. The beetles are not being killed by winter temperatures at high elevations anymore. In the past the beetles would be on the move for two weeks in July, now they can fly from July to October. They can reach more types of pines, the ones that live where it is colder. So what started with the Lodgepole pine then spread to the Jack Pine and the Whitebark, which don’t have defences against the beetle.

Dead pine in the Tetons, 2016

Dead pine in the Tetons, 2016

Finally, the recent western droughts have weakened the trees. This stresses the trees, making them less likely to fight off an invasion of beetles. The tree’s defences are slower when they are stresses, giving the beetles the advantage of time.

The Mountain Pine Beetles are a western species, but maybe not for long. Originally a beetle of Lodgepole pines, they were able to reach the Jack Pines where they found a new food source. The Lodgepole only lives in the west, but the Jack Pine covers much of Canada, stretching into the New England states.

Will the eastern pines begin to succumb to these beetles? Only time will tell, but the answer seems to be yes.

Rhododendron troubles

In 1993 a new species of water mold was discovered.  Currently named Phytophthora ramorum, this organism was isolated from rhododendrons in Germany and the Netherlands. Unsure of where it came from, it began appearing in multiple countries: Spain, France, Poland, Belgium, Sweden, Italy and the United Kingdom.

But it was not found on wild plants, it was on plants in retail nurseries. Specifically camellia and rhododendrons.

From the nursery plants it moved quickly into the forests. In the U.K. it killed Japanese larch (Larix kaempferi) plantations, Northern Red Oak (Quercus rubra), Beech (Fagus sylvatica), and Horse Chestnut (Aesculus hippocastanum).

In 1995 arborists in California began to notice that the Tanoaks were dying. It took until 2000 to find that the culprit was new water mold. Neighboring Oregon and Canada acted quickly, banning the import of  rhododendrons from California, which was a host plant that carried the mold but did not look sick. But the ban was not quick enough as in less than a year it would be found in Curry County, Oregon.

Things did not heat up for the nursery industry until 2004 when some west coast nurseries accidently shipped more than a million infected rhododendrons and camellia plants resulting in P. ramorum appearing in 22 states.

As a knee-jerk reaction to this accident, more states started regulating the import of plants from California. And the list of host plants began to grow. Washington lead with a conservative approach, requiring plants to be held for 24 hours to allow for inspection while Georgia banned all plants from California. By the end of the year an emergency federal order would regulate the movement of plants out of California, Oregon and Washington. California begins destroying nursery plants.

Other countries also feel the fear, banning the import of plants.

Notable Host Plants for Sudden Oak Death Seen at Retail Outlets
Hamamelis virginiana Witch Hazel
Camellia spp. All species of Camellia
Rhododendron spp All rhododendrons and azalea
Calluna vulgaris Scotch Heather
Pieris spp. All species of Pieris and Andromeda
Pseudotsuga menziesii Douglas fir
Viburnum spp. All species of viburnum
Cornus kousa Kousa dogwood
Syringa vulgaris Lilac
Magnolia spp. Many magnolia species

But was it all too late?

It was. Millions of Tanoaks, Coast Live Oak, California Black Oak, Shreve Oak and Canyon Live Oak died. It also damaged the Coast Redwood.

Why did it move so fast? P. ramorum was the perfect fit for the Pacific Northwest. This water mold loves cool, wet areas. The forests in the fog belt of coastal California and Oregon was heaven. It was also the perfect fit for a plant nursery, which also is cool and wet. Spread by spores, an unsuspecting person may carry it on their boots, car tires or even pets, furthering its reach.

“The water mold causing Sudden Oak death can be carried on boots, car tires or even pets that visit the west coast forests.”

In the United States the impact has been huge. The nursery industry has lost millions of dollars destroying infected plants and losing the ability to ship product. Property values have decreased as parks and homes lose their trees. These trees must be removed at the cost of the home owner. As the pathogen spreads, the Christmas tree industry will no longer be able to sell trees out of state.

Ecologically, the loss of the dominate Tanoak and Coast Live Oak has been detrimental to local ecosystems as the fire risk increased, wildlife has lost food and cover, and soil is exposed to erosion. Even the climate of the areas affected has suffered. The loss of trees has created a microclimate which changes what plants can grow in an area. This can cause problems decades in the future.

Scientists fear for the eastern oak forests as the infection in the United Kingdom has shown the Northern Red Oak to be in danger. It is estimated that the full impact of Sudden Oak Death will be in the tens of millions across the country.

More to come

The power of humans to disrupt local habitats is enormous. Through the movement of goods alone two key tree species has been wiped out with many more to follow. As the Ash and coastal Oaks succumb to their fate, it is up to us to stop this destruction.

It may seem bleak, but there is good news in the fight to save these trees, wildlife and our ecosystem. And there are things YOU can do to help. Come back next week to read PART TWO and learn how to keep the Sugar Maples in New England, the Hemlock in the Smokies, the Oaks on the West Coast and bring back the American Elm.

Paige Nugent

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