Helping Your Trees Survive the Drought

99.8 percent of California is suffering from some state of drought, and it is taking a toll on our trees.

Indeed, without concerted efforts, our state stands to lose much of its natural and urban forests. Unfortunately, the best thing for our trees – copious amounts of water – is not available. So, we must be creative, use our knowledge of tree biology and do what we can to give our trees the best chance of surviving this drought, and ensure they are in the best shape possible to withstand the next one.

Water Well

Use whatever water you have efficiently. Try to apply enough water to soak the upper 12 inches of soil, where most of a tree’s roots are located. Water the entire drip zone of the tree, but do not wet the trunk or surrounding soil excessively, as this may encourage bacterial and fungal growth. Do not spray the canopy of your trees with water as a significant portion of the water evaporates and never benefits the tree.

Prioritize Your Plants

When water is scarce, always allot the bulk of it to your trees. For one thing, your trees may take decades to replace, should they perish, while you can replace lawns and herbaceous ornamentals within a few months. The replacement value of trees is also considerably higher than the replacement cost and labor for most common ornamentals. So, if forced to choose between your oak trees and your rose bushes, water your oaks, sycamores and redbuds, but let the rose bushes die.

Lose the Lawn

Prioritizing your trees over your plants extends to the lawn. Not only is the water better allocated to your trees, but the lawn’s water needs are fundamentally different than those of your trees. Most mature trees desire infrequent, deep soakings, while grasses typically prefer frequent, light irrigation.

Frequent irrigation causes trees to develop shallow root systems. This not only causes stability problems, and predisposes the trees to failing in high winds; it prevents the trees from accessing deep water reserves. Many people are already making the switch from lawns to arid-adapted gardens or xeriscaping, which not only use less water, but they are better suited for living alongside your trees than a lawn is.

Mulch for Moisture

Mulch is an important tool for maintaining trees in wet periods; in droughts, it is indispensable. The mulch forms an insulating blanket over the roots, which keeps them from being scorched by the hot dry temperatures. Additionally, the mulch reduces the amount of water that evaporates from the soil, which keeps the soil damper than it would be without the mulch. Do not place the mulch directly against the trunk of the tree. Place a 2-inch-thick layer nearest the trunk, increasing to a 4-inch-thick layer near the drip line.

Get Creative

Try to collect and store as much water as possible, which you can use to water your trees. While it may be difficult to collect enough water to water a large, mature tree, scrounging for water can help you accumulate enough water to keep young trees healthy. Consider collecting gray water from your home or installing a rain cistern. When you use water for unusual tasks – such as filing a child’s swimming pool or changing the water in a freshwater aquarium – try to discard the old water inside the drip line of your young trees.

Going Forward

Use caution when deciding to plant new trees during droughts. It can be done, but young, yet-to-be-established trees require consistent watering to keep the root zone damp. If you decide to plant new trees, be mindful of the fact that the next drought may be right around the corner. Avoid planting trees that – even during wet periods — require supplemental watering, such as redwoods (Sequoiasempervirens) and red maples (Acer rubrum). Magnolias (Magnolia ssp.), cherry trees (Prunus spp.), birches (Betula spp.), gum trees (Eucalyptus spp.) and bald cypresses (Taxodium distichum) also require more moisture than Mother Nature provides to southern California.

Further Reading

See the following resources to find more information on keeping your trees healthy during the drought:


International Perspectives on the Drought

As the drought becomes more and more severe, and citizens and policy makers try to figure out mitigation strategies, it is helpful to examine the approaches that have helped other regions survive these parched periods. While it may not be advantageous to mimic their strategies in all respects, it is valuable to learn what has and has not worked in other places.

Australia has a long history of droughts, and the world’s driest habitable continent has developed a number of strategies that have helped the parched nation survive. Accordingly, Californian officials are now consulting with experts from Australia to help examine, analyze and implement some of the same measures that proved successful in the land down under.

Unfortunately, in an interview with US News, Daniel Connell, an Australian environmental policy expert, characterized California’s response to the drought as “absolutely pathetic.”

The Australian Drought

Whereas our current drought seems insufferably long to Californians who have struggled to survive the water shortage for over four years now, a particularly severe drought struck Australia from the years 1995 to 2012. This 17-year-long drought was the worst on record, and it forced the country to take significant steps to weather the crisis.

Unlike in California, where much of the emphasis has centered around simply surviving until the rains return, Australians took the opportunity to make significant change. This is an important point for Californians to consider – more droughts will come, and we should use this current drought to prepare for the future. As explained by Rebecca Nelson, senior fellow at the University of Melbourne, School of Law, “Don’t waste the crisis.”

In Australia’s case, they implemented a variety of strategies to help not only survive the drought, but to alter their way of life. Some of the measures they adopted include:

  • Policy makers enacted water restrictions that lowered the daily per capita water usage to 55 gallons. For comparison, Californians use approximately 105 gallons of water each day.

  • Policy makers imposed hard caps on the amount of water that could be drawn from a given river basin.

  • In contrast to water restrictions imposed on U.S. soil, which are typically enacted at the local or state level, Australia’s federal government imposed the country’s water restrictions.

  • Australia built several desalination plants and the accompanying pipelines to carry the fresh water, but most of these lay idle now, as the country is experiencing a “wet” period.

  • Australia imposed significant water restrictions on the agricultural sector.

  • Because information and water usage data is so crucial for effective water management, the Australian government began metering water usage, thereby enabling adjustments and reallocations of water supplies.

  • Australia now trades water as any other commodity, such that the price of water reflects its availability. This provides an economic pressure that tends to deter overuse and waste.

  • Finally, and perhaps most importantly, Australia kept most of their water-saving strategies in place once the drought ended. This has fostered a change in the national attitude toward water, and helped the country prepare for the inevitable droughts in the future.

Picking Priorities

Droughts inherently cause tension between the environment and the economy.

For example, according to the Public Policy Institute of California, the state uses water in three primary ways. Fifty percent of the state’s water is used for environmental purposes, such as keeping reservoirs and rivers sufficiently full and ensuring habitats have enough ground water to remain healthy. Forty percent of the states’ water supply is dedicated to agricultural activities, and about 10 percent is provided to urban areas, who must import water to meet their needs.

Of course, those living in urban areas should strive to reduce their water consumption — it would be foolish not to take such steps. However, urban water usage only represents 10 percent of the total water budget. Even a 50 percent reduction in water usage by every man, woman, child and corporation would only result in a 5 percent reduction in total water usage. The bulk of the savings can only come from that allotted to agricultural uses or for the environment.

It is easy to see that it may be economically advantageous to allot more water to the agricultural industry during times of drought, but it is essential to ensure the environment has enough water to remain healthy. Wisely, Australia valued its urban forests during their drought and prioritized them when allocating water. By continuing to support their trees, Australians helped mitigate some of the drought’s effects, as trees help cool the atmosphere and block desiccating winds.

Additionally, as trees cannot be replaced as quickly as lawns and ornamental plants can, it is important to protect the existing forests and other habitats, which will not regenerate quickly if allowed to perish.

The End May Be In Sight

Hopefully, just as Australia managed to survive its drought (and set themselves up for a better future), California will learn to endure the current drought.

One thing that may help reverse the Golden State’s fortunes is the development of an El Nino weather pattern. You can read a deeper explanation of the El Nino phenomenon here, but simply put, El Nino events feature increased water temperatures and atmospheric air pressures in the eastern Pacific Ocean. When these changes occur, it has significant effects on the world’s weather. One of the typical effects is increased rainfall in California.

El Ninos occur on a cyclical basis, and, fortunately, meteorologists are seeing the pattern develop now. Some predict that the phenomenon will bring increased rains to California during the summer, and these may continue throughout the fall and winter as well. While this rainfall will not be sufficient to end the drought completely, it will surely help take the edge off.

It is important to note that El Nino events can be difficult to predict, as many meteorologists forecasted an El Nino event last winter, and it failed to materialize. Ironically, while El Nino events bring increased rains to California, they can cause droughts in other regions, such as – you guessed it — Australia.

rain barrel

Low Impact Development at the Landowner Level

Urban runoff is the largest cause of ocean pollution in southern California. Our many roads and sidewalks whisk the polluted water from our highways and byways right into the ocean, via a network of storm water drains.

These pollutants include not only the oils, phosphates and plastics littering local streets, but also the pesticides, herbicides and fertilizers that drench local lawns.

One of the best ways to address these problems and stop the flow of pollutants is to manage storm water runoff more effectively. To that end, developers and environmentalists have developed a philosophy called Low Impact Development (LID), which seeks to treat runoff water on site – rather than discharging the polluted water into the ocean.

Pollution Solution

Ideally, the city of Los Angeles will enact a low impact development ordinance that would help protect our local waterways. Doing so will require new developments to utilize low impact development principles in new construction projects. Additionally, the ordinance would provide local authorities with enforcement capabilities to help ensure the long-term stability of the movement.

By simply implementing LID principles on public lands and right-of-ways, the City of Los Angeles could reduce a significant portion of the runoff water problem. According to Community Conservancy International, employing LID principles on the city’s publicly owned lands would eliminate approximately 40 percent of the city’s runoff water problems.

Low Impact Locals

While it seems likely that an LID ordinance will eventually come to fruition, the problems associated with runoff water continue to multiply. Accordingly, conscientious landowners should begin installing LID systems wherever practical.

No matter how large or small your property is, you can implement low impact development and become part of the solution.  Whether you own a single-family residence or a 1,000-unit industrial complex, LID principles help you to help the planet.

Personalized Solutions

The best strategies for your site depend in large part on the specific characteristics of your land and its place within the water shed. However, many Best Management Practices (BMPs) – defined by the Environmental Protection Agency as those techniques and structures that reduce surface runoff pollution – work in most locations.

Some of the most popular BMPs include:

  • Vegetated Swales

  • Tree Wells and Curb Bump Outs

  • Rain Barrels

  • Permeable Pavers

  • Rain Gardens

  • Gravel Gutter Seams

  • Retention Ponds

  • Increased Tree Plantings

Nevertheless, some strategies are inappropriate for some locations. The soil in some areas is not conducive to water infiltration, and the basements in many residential areas extend to or beyond the sidewalk. In such cases, it may be advisable to capture and reuse rainwater, rather than encourage infiltration. However, both strategies are consistent with LID principles, as the rainwater is managed on site.

Low Impact Incentives

Unfortunately, the City of Los Angeles does not currently provide economic incentives for landowners who install low impact development equipment or features on their land. The city bases storm water pollution fees on the density of the parcel, not the amount of runoff water produced by the land, as is the model in use in many European cities.

Nevertheless, LID projects are usually less expensive to install than traditional water management solutions are, which provides you with immediate savings. Even in rare cases in which LID solutions end up being more expensive than traditional designs, you can take pride in the fact that you are helping to clean up the ocean, and making your neighborhood more attractive, environmentally friendly and progressive, than those who wait for the authorities to address the problem.

rain garden

Low Impact Development for Los Angeles: The Dollars Make Sense

One of the most exciting things about low impact development projects is that they usually save developers and communities money.

In fact, according to a 2007 study by the Environmental Protection Agency, which examined the costs of construction projects that incorporated LID design principles across the country, LID projects are typically less expensive than construction projects that utilized traditional water management strategies.

Details of the Study

The EPA study – which only considered capital costs, and did not examine the social, environmental or communal benefits provided by LID – found that most LID projects cost only 15 to 80 percent as much as those projects that relied on traditional water management strategies.

You can download the entire study here (PDF), but a few examples include:

  • Auburn Hills – a residential community in southwestern Wisconsin – was constructed in a clustered fashion, to protect and retain green spaces. The project utilized several LID principles, and cost the developers approximately $1.6 million. If the developers had utilized conventional water management techniques, the neighborhood would lack the aesthetic appeal and small ecological footprint that it enjoys. Additionally, if the developers had utilized traditional storm water management strategies, the project would have cost an estimate $2.36 million. Therefore, the developers saved approximately three-quarters of a million dollars (32% savings) and built a superior subdivision in the process.

  • Developers utilized LID principles when designing a conservation-minded, mixed-use development in Mill Creek, Illinois. By incorporating vegetated swales, leaving many natural areas intact and using more permeable surfaces than traditional strategies call for, the developers constructed each lot for approximately $9,000. If traditional water management strategies had been used in the construction process, each lot would have cost $12,000 to prepare.

  • By using low impact development principles, Bellingham City, Washington enjoyed incredible savings during a parking lot renovation project. Rather than spending an estimated $27,000 on the project by installing large underground storage vaults to contain rainwater, they utilized rain gardens to absorb runoff water and completed the project for a measly $5,600 and change. In this extraordinary case, LID principles allowed the city to reduce capital costs by 80 percent.

While usually effective and affordable, LID is not a magic bullet, suitable for every property and community. LID principles can raise the costs of construction in some rare instances, so it is important to examine such decisions carefully. For example, a project in Kensington Estates, Washington incorporated LID principles, but the costs were twice as high as they would have been, had they elected to employ traditional techniques.

Ancillary Benefits

Because LID principles allow plants and trees to do the heavy lifting, such areas are invariably greener than they would otherwise be. In addition to the serving a greater good and helping to protect southern California’s habitats and climate, communities and properties featuring low impact development principles enjoy a variety of direct benefits. For example, well-planted properties demand higher sale prices than similar properties that lack these natural amenities.

According to a 2010 study in Portland, Oregon, homes with street trees sold for an average of $7,000 more than those homes without street trees. However, even those that had no street trees – but were adjacent to homes with trees – sold for about $1,600 more than comparable homes.

Additionally, trees and natural landscapes provide cultural benefits (such as reduced crime rate), health benefits (including decreased recovery times and lower stress levels) and create “green collar” jobs.

Funding Strategies

With luck, the City of Los Angeles will enact a LID ordinance, which will require newly constructed roads and other infrastructural components to incorporate Best Management Practices (BMPs) – which are those items and strategies that reduce runoff water pollutants — in their designs.

However, to enact such ordinances, city officials must first allocate – or prescribe a mechanism to generate – funds for enactment and enforcement. Additionally, while BMPs will usually lower the costs of new construction projects, funding is necessary for BMP installation in existing properties.

A 2009 report, entitled “Green Infrastructure for Los Angeles: Addressing Urban Runoff and Water Supply Through Low Impact Development,” by Haan?Fawn Chau, of the University of California, Los Angeles, addressed some of these issues. According to the report (PDF), numerous funding strategies are feasible, including:

  • Establishing a one percent tax on new construction

  • Installing parking meters in suitable locations

  • Private Foundation Grants

  • Federal and State Grants

  • Constructing new parks and utilizing the Quimby fees for LID projects

  • Corporate sponsorship

  • Public-Private cooperative efforts

  • Parcel drainage fees (IPAs).

All of these approaches have benefits and drawbacks, which should be the subject of vigorous, informed debate by all stakeholders – including the general public. However, the important thing is that a funding method is selected and low impact development approaches replace traditional storm water runoff management techniques.


Low Impact Development: Best Management Practices

Storm water runoff is a significant environmental problem for the Los Angeles area, as it contributes to ocean pollution and exacerbates drought conditions. Low impact development (LID) is a development strategy that seeks to manage storm water runoff more effectively by dealing with runoff water on site, rather than trying to channel the water away as quickly as possible.

Low impact development principles embrace and utilize a variety of specific techniques and structures to accomplish this task. The United States Environmental Protection Agency uses the term “Best Management Practices,” or BMPs, to refer to some of the best-suited techniques and structures, for reducing the amount of surface pollutants carried by storm water runoff.

Vegetated Swales and Rain Gardens

One of the simplest ways engineers and city planners can help reduce runoff water is to break up extensive paved areas with small “islands” of vegetation. This allows the plants to absorb and store the water, before ultimately releasing it back into the atmosphere. Most often, these areas are installed in low-lying areas, to take advantage of the natural lay of the land.

Rain Cisterns

Rain cisterns are valuable tools for managing rainfall and reducing an area’s runoff water. By storing rainwater, rain cisterns transform the surplus water from a liability to an asset. Cisterns collect the water pouring out of downspouts, thereby reducing the amount of storm water filling sewers and collecting pollutants. Additionally, they serve as a source of clean water, suitable for watering lawns, irrigating crops and other outdoor uses.

Green Roofs

At first glance, the notion of sod-covered roofs (pictured above) seems like a joke. However, upon closer examination, it becomes obvious that the concept has many merits. The grass absorbs most of the rainfall landing on the roof, which helps to address runoff water problems, and it helps to keep homes cooler in the winter, courtesy of the insulating value of the plants and soil. Additionally, as the grass transpires – drawing water from its roots and releasing it into the atmosphere – it lowers the local temperature further.

Permeable Pavers and Pavement

Some places simply require extensive paved areas; shopping malls, municipal centers and grocery stores are rarely feasible without large parking lots and pavement. Fortunately, engineers have devised a solution for these areas, called permeable surfaces. Unlike traditional surfaces composed of solid concrete or asphalt, permeable pavements allow water to trickle through them, rather than run across the surface.

Curb Cuts and Bump-Outs

Curb cuts are a brilliantly simple solution to storm water. Whereas conventional curbs contain water, preventing it from reaching the vegetation and soil a few short inches away, curbs designed with low impact principles have periodic gaps cut into them. These cuts allow water to pass through to the planted areas, reducing the overall volume of water flowing along the curb, and use it in the immediate vicinity to water plants and trees.

Tree Installations

Simply planting medium or large canopy trees along sidewalks and roads drastically reduces the amount of runoff water in the area. Trees absorb water from the soil, use what they need and allow the excess to evaporate into the air via small holes in the leaves. This process not only manages runoff water, but it provides all of the other benefits trees do, such as shading the area, cooling the environment through the process of transpiration, improving the aesthetics of the area and raising property values.


Low Impact Development: Ecological Solutions to Concrete Problems

Despite recent efforts to reduce carbon emissions and protect green spaces, the natural world continues to struggle as it attempts to cope with human development.

The climate is changing, oceans are becoming increasingly acidic, habitats – and the species native to them — are disappearing and, perhaps most importantly for Californians, our fresh water reserves are proving insufficient to satiate a thirsty metropolitan area.

Timescale of the Trouble

Solving these problems will not happen overnight. It is going to take decades of effort to undo the damage caused over the last century. This is an unfortunate fact, but it highlights an important lesson.

One of the best ways to solve a problem of tomorrow is to avoid it today. We can do little to change some of our existing problems, but we absolutely must make changes to the way we construct buildings, cars and cities, moving forward.

Fortunately, civil engineers, architects and city planners are beginning to understand this, and develop techniques and strategies that help reduce some of these problems.  Many of these new approaches specifically address the problem of storm water management, which is a common cause of many of California’s current challenges.

Low Impact Development

One of the best strategies for helping to clean up the environment is called Low Impact Development, or LID.

Low impact development is a storm management strategy that turns conventional storm water management methodology on its head. Whereas civil engineers historically sought to collect and channel runoff water, aiming to transport the water from the city to the ocean as quickly as possible, low impact development principles embrace a more effective solution that relies on the contributions of plants, trees and healthy soils.

LID strategies not only accomplish the targeted task – managing storm water more effectively — they do so without creating new ecological problems. In fact, LID strategies improve the health of the local environment in a variety of ways. They also help solve a number of tangential problems, such as reducing the amount of surface pollutants reaching the ocean.

Additionally, because LID strategies and techniques often emphasize the retention of natural areas, they help improve the aesthetics of most areas in which they are implemented.

Problems with the Current Paradigm

Hundreds of years ago, rain falling over Los Angeles – which was a more common occurrence than it is in these drought-stricken times — did not cause environmental problems. The ground absorbed what it could, while the rest followed the path of least resistance, and made its way to creeks and rivers.

Along the way, forests and wetlands absorbed much of this water, which kept the plants healthy and greatly reduced the rate at which rainwater flowed into the ocean. These vegetated areas also helped to store a significant portion of the runoff water, which reduced the number of erosion-related problems along the way, and reduced the amount of sediment and nutrients that reached the ocean.

By contrast, rain falling over modern-day LA often largely lands on impervious surfaces. Unable to absorb much – if any – water, the concrete and steel skeleton of our city carries the runoff away with devastating efficacy.

Confined to concrete channels and storm drains, the water cannot replenish the wetlands and forests as it once did. Instead, it leaves these habitats parched, causing stress for the plants and animals living within them. As these habitats dry out, the surrounding atmosphere dries out too, which often leads to reduced rainfall and exacerbates the extent and severity of droughts.

Low Impact Innovations

Low impact development principles solve most problems created by traditional approaches. Often, those engineering LID projects have stolen their strategies directly from the natural world. Like so many other good ideas, Mother Nature figured out this approach first.

The basic strategy is simple: Instead of channeling the water to the ocean like a high-speed train, slow it down as much as possible, and try to get rid of as much of it as you can along the way.

Fortunately, implementing LID principles is relatively easy. In a nutshell, you place an assortment of plants, trees and plenty of soil in the water’s path and let nature take its course.

Trees and plants not only absorb and store vast quantities of water, they also release water into the atmosphere as part of the process of transpiration. During these processes, the roots and microorganisms living in the soil filter out many harmful pathogens and pollutants.

By incorporating these “living sponges” into the design of cities, buildings and neighborhoods, the amount of runoff water exiting the compound is drastically reduced, and the local environment becomes cooler and more humid. Such areas require only modest maintenance, they are economically feasible to construct, and, they look great.

You can learn more about implementing low impact development principles in Los Angeles in this report (PDF), authored by Haan‐Fawn Chau, of the University of California, Los Angeles. Additionally, the United States Environmental Protection Agency has produced this fact sheet, which provides an overview of LID.

curitiba street

Trees: A Neglected, but Essential Component of Municipal Infrastructure

Nearly 6,000 years ago, in what is now Iraq, the Mesopotamians took an important step that would forever change the world: They turned the region’s well-worn footpaths, born of countless generations’ foot traffic, into the first stone-paved roads. In doing so, they enabled goods and services to flow easily through the region, and the civilization prospered. Many years later, humans civilization is utterly dependent on these and similar resources.

Today, we call these types of common goods “infrastructure.” Other examples include canals, reservoirs, dams, bridges, and tunnels. They are those things that make life easier for all citizens, and are often provided and maintained by local municipalities.

Gray vs. Green

Infrastructural assets are often divided into two different classes. “Gray” infrastructure includes those things made from concrete, plastic or steel, such as buildings and transportation routes. On the other hand, “green” infrastructure refers to living entities, such as rain gardens and street trees.

While the two classes have obvious dissimilarities, they provide similar infrastructural value, often at a lower cost to the taxpayer. For example, most major municipalities must implement and maintain a system for dealing with storm water runoff – a task that can be accomplished with gray assets (for example, a sewer system), green assets (such as rain gardens, street trees or wetlands) or – as common sense dictates – a combination of both gray and green solutions.

The Advantages of Incorporating Green Infrastructure

While civilization is unlikely to ever jettison sewers, bridges and dams completely, street trees, wetlands and other green infrastructure projects offer numerous benefits that traditional strategies do not. For example, trees and plants improve the quality of the air and reduce local temperatures through the process of transpiration. Virtually any tree installation will help reduce the area’s runoff water, but projects specifically designed to divert, absorb or store water – such as rain gardens – are especially helpful in this regard.

Additionally, while roads, dams and bridges usually fail to improve the aesthetics of an area, living plants and trees almost invariably make an area more beautiful. This increased aesthetic appeal translates to greater demand for local properties, which increases home values.

Empirical Evidence

It is important that green infrastructure projects are elegantly planned and suitably maintained. One challenge to implementing natural solutions is the perception that trees are an expensive and damaging resource, which will cause municipalities to pay more than they will save.

According to a recent study, nothing could be further from the truth.

Conducted by the American Society of Landscape Architects, American Rivers, the Water Environment Federation and ECONorthwest, the study examined almost 500 different green infrastructure projects in the United States. The researchers concluded that the majority of the projects (75 percent) cost the same or less to implement and maintain as similar, gray infrastructure projects did.

The study’s authors also determined that green infrastructure projects help cities use less energy and promote greater health among their citizens. This occurs as trees and their roots help filter bacteria and other pollutants from local waterways.

Additionally, many city managers and strategic planners worry that trees and plants will damage hardscapes, through the destructive action of their roots. However, as explained in a 1998 paper by Professor Kim D. Coder of the Warnell School of Forestry Resources, many problems blamed on trees are more appropriately placed at the feet of flawed hardscape designs.

From the study:

“Many infrastructures that concentrate and transport required resources for people are poorly designed and built to withstand natural processes over time. These engineering flaws are exacerbated by opportunistic tree roots colonizing new resource spaces.”

Simply put, better designed sidewalks and subterranean features will result in less damage from tree roots.

The Takeaway

The bottom line is that distinguishing between gray and green infrastructure is not always helpful – they both provide value for citizens and require resources to maintain. Moving forward, stakeholders must consider the empirical evidence and proceed deliberately, carefully considering all available strategies for coping with municipal challenges. Some solutions are better met with the help of trees, while others are more appropriately addressed through the construction of traditional infrastructural components.

The Asian Citrus Psyllid: An Exotic Pest Threatens California’s Citrus Industry

Invasive pests and fungi are some of the deadliest threats to many trees. Because the trees under attack have not evolved mechanisms to combat the alien attackers, significant losses can occur very quickly.

Unfortunately, California’s citrus trees are currently under threat from just such a pest, known as the Asian citrus psyllid (Diaphorina citri). First documented in Florida in 1998, psyllids have significantly damaged the state’s citrus production. Recently, the state destroyed 250,000 acres of trees in a desperate attempt to regain control. (Valentine, 2014) Time will tell if their efforts were in vain.

Plenty of Precedent

Unfortunately, history amply demonstrates the damage exotic species can cause.

Around 1900, a pathogenic fungus of Japanese origin arrived on American shores. The fungus, known as chestnut blight (Cryphonectria parasitica), soon began killing American chestnut trees (Castanea dentata) at an alarming rate. In as little as 40 years, the trees essentially disappeared. While a few scattered individuals cling to life, scientists are still trying to solve the problem and save the species that formerly dominated eastern forests.

A more recent example comes in the form of an Asian beetle, called the emerald ash borer (Agrilus planipennis). During the larval stage, these beetles feed on the inner bark of the trees. This destroys the tree’s ability to transport water and nutrients up and down the trunk, ultimately killing the tree. First documented near Detroit, Michigan in 2002, the beetle has spread throughout most of the eastern United States, killing tens of millions of ash trees along the way.

The Bad News Bug

Psyllids damage citrus trees through their feeding behavior. Like the other members of the family Hemiptera, these eighth-of-an-inch-long insects are “true bugs,” who feed via piercing-sucking mouthparts. When feeding, they pierce the surfaces of leaves and then suck out the sap on which they feed. In addition to the trauma caused by their mouthparts, psyllids inject toxic saliva into the plant, which causes further harm.

These insects have hitchhiked around the world, colonizing the Middle East, Central America, South America, Mexico and several Caribbean Islands, along its way. Since colonizing Florida, Asian citrus psyllids have spread to Louisiana, Georgia and South Carolina as well.

While California’s psyllid problem is not yet as dire as Florida’s is, the destructive bugs have been documented in nine counties within the state. So far, psyllids have not yet colonized many of the most important commercial citrus groves, but without an aggressive response, the problem is sure to grow over time.

Even Worse News Bacteria

The invasive insects are only half of the problem. Psyllids in many parts of the world harbor bacteria that cause “Citrus Greening Disease,” also known as Huanglongbing (a Chinese term, which translates to “Yellow Dragon Disease”). The bacteria– known as Candidatus Liberibacter asiaticus* – infects the phloem of citrus trees. Among other problems, the bacteria cause twigs to die, trees to bloom off-season and a general decline in health and vigor. Additionally, the bacteria cause trees to produce green fruit, thus giving the disease its common name.

After years of nervously watching cases appear in Baja, Mexico, California researchers found what they feared. In March of 2012, samples from a single tree in a residential yard in Hacienda Heights tested positive for the problematic bacteria. Fortunately, this is the only documented case in the state, but it is unlikely to be the last.

Hope on the Horizon

A cure for Huanglongbing still eludes scientists, but they continue to attack the problem. Some trees have responded to treatments for a brief time, but they all succumb eventually. To help prevent the spread of the disease, the United States Department of Agriculture has imposed a quarantine, banning interstate commerce of citrus trees from the nine infected counties.

Nevertheless, it is ultimately preferable to control the insects that spread the disease. The insect itself causes damage, but it is also the vector for the debilitating bacteria.

Biological control efforts may offer some relief in the future, as several animals parasitize (and ultimately kill) psyllids in their native lands. Scientists have released two different ectoparasites of the psyllids in Florida: Tamarixia radiata and Diaphorencyrtus aligarhensis. Both insects have proven effective in reducing local psyllid populations, but further research is required to determine the viability of the solution in other locations. Over the past few years, scientists in California have released 75,000 Tamarixia radiata. (Lopez, 2013)

*Interesting note: The tern “Candidatus” refers to the fact that these bacteria have not yet been cultured in a laboratory.


Lopez, R. (2013, August 4). Citrus growers use predator wasp to fight disease threat. L.A. Times.

Valentine, K. (2014, November 6). ASIAN CITRUS PSYLLIDS FOUND IN GROVE NEAR EXETER. ABC Action News.

medicinal photo

Growing Healthcare: Medications Made from Trees

As most elementary school science worksheets explain (complete with bolded vocabulary terms and the same tired examples offered when you were in elementary school), trees are a renewable resource that provide humans with the raw materials for making finished goods like lumber, paper and pencils.

The thrust of the lesson is true enough, but it sells trees short. Take the examples of finished goods; while lumber and paper are certainly important for modern civilization, trees have yielded products that are arguably even more important: medications.

From pain killing bark extracts to cancer-killing compounds, trees produce a number of important tools that are helpful in the fight against suffering and disease.

Oh, My Aching Bark

The primary active ingredient in aspirin is derived from the bark of willow trees. Although first produced in its modern form by Bayer in 1899, humans have used willow bark extracts for pain relief since 400 B.C.

The bark itself is a popular herbal remedy for a variety of ailments, including back pain, inflammation and toothaches. The amount of salicylic acid — the active ingredient in the willow bark – varies from one species to the next. White (Salix alba), purple (Salix purpurea) and crack willows (Salix fragilis) are among the species with the highest proportion of the salicylic acid, and they are most commonly used to manufacture aspirin.

Some birch trees (Betula ssp.) also contain salicylic acid, although they are not used the commercial manufacture of the drug. However, folk remedies commonly encourage the chewing of birch twigs to relieve pain.

Taxus Treatment

Some trees are important allies in the fight against cancer. In 1962, researchers working at Research Triangle Institute’s Natural Product Laboratory in Research Triangle Park, NC, found that extracts from the bark of Pacific yews (Taxus brevifolia) exhibited cytotoxic (cell-killing) characteristics in laboratory tests.

Eventually, researchers identified the active chemical from the bark, called paclitaxel.  By 1977, paclitaxel had demonstrated anti-tumor activity in mice. Unfortunately, paclitaxel was difficult to synthesize at the time; but after developing a way to extract the precursor to paclitaxel from the bark of the common yew (Taxus baccata) – which is very common – production began to ramp up.

To date, the National Cancer Institute states that, Taxol (the proprietary name for the drug) is the “best-selling cancer drug ever manufactured.” (National Cancer Institute)

Sacred Bark

Native to the Western United States and Canada, the cascara tree (Rhamnus purshiana) has been an important medicinal tree for hundreds of years. Often called the Cascara Sagrada (“sacred bark” in Spanish), the tree produces compounds – known to chemists as hydroxyanthracene glycosides – that work as natural laxatives.

Scientists continue to learn new things about the cascara tree and the medical benefits it may offer. For instance, some evidence has suggested that another compound in the bark – emodin – may exhibit both cancer- and virus-fighting abilities. (Dang Shuangsuo, 2006) (Gopal Srinivas, 2003)

Malarial Medicines

One of the most important diseases in the history of Homo sapiens, malaria is a deadly parasite that continues to threaten those living in tropical locations. While often produced synthetically, quinine is a very old malaria medication, which is derived from the bark of several trees of the genus Cinchona.

During the Civil War, quinine was a difficult substance to obtain. In response, doctors of the time turned to a common North American species: the flowering dogwood (Cornus floridana), whose bark also produces antimalarial compounds.


Dang Shuangsuo, Z. Z. (2006). Inhibition of the replication of hepatitis B virus in vitro by emodin. Medical Science Monitor.

Gopal Srinivas, R. J. (2003). Emodin induces apoptosis of human cervical cancer cells through poly(ADP-ribose) polymerase cleavage and activation of caspase-9. European Journal of Pharmacology.

National Cancer Institute. (n.d.). Success Story: Taxol® (NSC 125973). Retrieved from U.S. National Institutes of Health:

Trees, Jobs and the Economy


It is abundantly clear that trees help people to feel good, heal fast, keep cool and stay safe; but can they help the bottom line? According to the available evidence, trees are unquestionably good for reducing costs and increasing profits. In fact, because of the perpetually warm temperatures of Southern California, Los Angeles area merchants are among those who stand to benefit the most from capitalizing on the economic benefits of trees in their operations.

Preempting the Pushback

Retail merchants often worry that trees will reduce their store’s visibility or require additional labor to maintain. While it is understandable that they do not want to impair marketing efforts or waste employee time sweeping up leaves, such problems are often overstated. In practice, careful species selection and proper pruning can eliminate many visibility problems. Many cultivars are available that do not exhibit the litter problems associated with the wild species. For example, non-fruiting sweetgum (Liquidambar styraciflua) cultivars do not produce the woody “spike balls” for which the species famous.

Utility Usage

If planted in a well-conceived manner, trees reduce heating and cooling costs. Consider, for example, a large retail shop with a large, south-west-facing wall. This wall absorbs the sun’s most intense rays, and causes a sharp rise in summer cooling costs. Now, imagine the same building, but with a row of trees along the exposed wall. The trees not only provide shade, but they create a cooling effect on the environment through the process of transpiration. A 2002 study by H. Akbari provides some of the most compelling evidence that trees help reduce utility costs. According to the study, the annual electricity savings of an office building surrounded by three trees amounts to between 10 and 35 dollars for every 100 square meters of roof area. (Akbari, 2002)

Air-Conditioned Asphalt

Trees in parking lots are beneficial as well. According to a 1999 study of trees in Davis, California, trees significantly improved the parking lot environment. The study, which was published in the “Journal of Arboriculture,” found that trees reduced the ground-level temperatures by as much as 36 degrees Fahrenheit. (Klaus I. Scott, 1999) This undoubtedly leads to a better customer experience, which encourages return visits.

Money Does Grow on Trees

Trees do not just reduce costs; they actually attract and help retain customers. According to study, after study, after study, customers prefer well-planted shopping areas to those without trees. The Ontario Heritage Tree Alliance has published a partial list of the economic benefits that accompany trees, including those that relate to retail sales. The Alliance cites a 1999 study that found that consumers were willing to pay more for parking, goods and services in well-planted business districts. (Heidenreich)

Trees Don’t Trim Themselves

On the other side of the equation, trees create an abundance of jobs as well. In 2009 alone, California ReLeaf put $3.3 billion in employee pockets. Because the jobs associated with trees are so diverse, it is difficult to estimate how many people nationwide are employed by trees in some fashion (check out this list of 50 tree-related professions by the Tree Foundation of Kern, a non-profit group that works with urban forests).   According to the U.S. Bureau of Labor Statistics, 40,000-odd people were employed as tree trimmers or pruners in 2013. However, this number represents only a percentage of those who work in tree care, as the Bureau does not include self-employed tree trimmers in its statistics. (U.S. Bureau of Labor Statistics, 2013)


Akbari, H. (2002). Shade trees reduce building energy use and CO2 emissions from. Environmental Pollution.

Heidenreich, B. (n.d.). The VALUE OF TREES: Making the Case for Tree Protection. Retrieved from


U.S. Bureau of Labor Statistics. (2013). Tree Trimmers and Pruners.