Regardless of the urban spaces and the technotopes we live in, if the forests go, we go too. And the forests are not doing well. In Hawaii, seemingly ubiquitous ohi’a trees have been dying at an astonishing rate since 2010. These are the US’s only rain forests. If the trees collapse, the whole native ecosystem goes with it. Nearly 50.000 acres of native forest on the big island are infected with rapid ohi’a death disease. It threatens the whole family of metrosideros trees and shrubs which are found mainly in the Pacific (see here). The plight of the ohi’a is not unique. It is part of a crisis playing out in forests all over America. Drought, disease, insects and wildfire are chewing up tens of millions of trees at an incredible pace. Much of it is driven by climate change.
Many of us do not lose sleep over this silent murderous transformation, although mankind’s fate depends on healthy forests. Since the time the first hominids walked across the African savannah until this very day, we have always been dependent on trees. Now climate change is destroying them. Not only do we fail to lower our emissions, climate change is also endangering our natural carbon and methane sinks. The problem is becoming more unsolvable by the day. Growing forests is a very good strategy for creating carbon sinks, but if the trees are not healthy and the forests die, the problem only gets worse. It is not only that we fail to address some problems – higher seas, new weather patterns, droughts and floods. It is a steady accumulation of hundreds of problems, many of which were never foreseen and most of which are unsolvable. Our planet will change beyond recognition. Our societies need to adapt to factors which are out of control. The ecological crisis leads to social and political crises
California and the mountain states have suffered particularly big die-offs in recent years, with 66 million trees killed in the Sierra Nevada alone since 2010, according to the Forestry Service. In northern California, an invasive pathogen called Sudden Oak Death is infecting hundreds of different plants, from redwoods and ferns to backyard oaks and bay laurels. Once infected, the plants die within two to five years. In Hawaii, warming spread four types of beetles that bore into the ohi’a bark. The beetles carry disease spore on their wings, in their guts and in the sawdust of burrows, spreading it from tree to tree. The numbers of these beetles of the scolylinae family are exploding around the world. They appear unstoppable: spraying each tree with insecticide would be made futile by rain and pheromone-laced traps appear ineffective (see here).
Five full years of drought in the West starved trees of water, weakened their defences and created conditions for ‘insect eruptions.’ Bark beetles and mountain pine beetles, usually held in check by wet winters, now have more time to breed and roam. The latter have already expanded their range from British Columbia across the Rockies, to the Yukon border and eastward, into jack pine forests that have never seen any of these insects. Due to climate change, insects become exotics in native forests they have never lived in before. The outcomes look dire. In the redwoods, the loss of nut-producing species leave birds and mammals that rely on them without food. The loss of mountain pines threatens grizzly bears and the critical snowpack that supplies water to life below (see here).
Picture 1: Pine trees dying in the Smoky Mountains (Source: Google Images).
Pine beetles have damaged more than 1.5 million acres of forest in Colorado and spruce beetles have damaged more than 2.5 million acres in Alaska. Invasive plant species displaces important native vegetation because the invasive species often lacks natural predators. Climate change often benefits invasive plants, since they are generally more tolerant to a wider range of environmental conditions than are native plants (see here).
There is also the growing problem of wildfires. In recent years, wildfires consumed more than 28.000 square km of forests. Climate change is projected to increase the extent, intensity and frequency of wildfires. Aside from all this, there are hurricanes and wind storms. The hurricanes Rita and Katrina in 2005 damaged a total of 5.500 acres of forest. The amount of carbon released by these trees as they decay is roughly equivalent to the net amount of carbon sequestered by all U.S. forests in a single year (see here). Here go our carbon sinks. Globally, deforestation is a hugely significant contributor to climate change. It has been estimated that forest loss and other changes to the use of land account for around 23% of current man-made CO2 emissions – this equates to 17% of the 100-year warming impact of all current greenhouse gas emissions (see here).
Forest health and the CO2 cycle
Plants absorb CO2 from the air as they grow. They use energy from the sun to turn the carbon into building blocks for their trunks, branches and foliage. In fact, mature forests do not necessarily absorb much more CO2 than they release, because when trees die and either rot down or are burned, much of its stored carbon is released again. This is why the Amazon rain forest, once the world’s great green lung, is now a net producer of CO2. The most important quality of mature forests is not that they reduce the amount of CO2 in the air, but that they constitute huge reservoirs of stored carbon.
If, on the other hand, trees are planted, they will soak up CO2 as they grow, reducing the amount of greenhouse gas in the atmosphere. It is thought that trees, plants and other land-based carbon sinks currently soak up more than a quarter of all anthropogenic CO2. The problem is that, as climate change alters the frequency and intensity of forest disturbances, such as insect outbreaks, invasive species, droughts wildfires, and storms, the ability of forests to act as carbon sinks decrease. If the trees become sick or die, they turn into a source of carbon. As it turns out, many tree species seem to be extremely vulnerable to temperature change. Evans et al. explained in Ecology Letters that – contrary to what many deniers say – the more the climate is warming, the slower trees and many other plants are growing (see here). Warmer temperatures stimulate tree growth in the short term, but there is a tipping point beyond which any more heat is detrimental. When the growth rate of trees slows down in response to environmental stressors, they can get by for a few years, but over time they deplete their resources and become much more susceptible to additional stress. Eventually, the heat stresses trees beyond their breaking point (see here).
This has been empirically observed. In the southwestern United States, as well as the interior of Canada and Alaska, forests could see up to a 75 percent slower growth rate thanks to higher summer temperatures. The vast boreal forests of Alaska had been projected in major climate models to flourish and become greener as the planet warms. Instead, they are browning. The previously assumed positive influence of warmer temperatures on boreal forests is nowhere to be seen (see here).
Researchers used laser-imaging technology mounted to a plane to map the tree health of California’s forests after four years of drought. The snapshots reveal how much water content the forest canopy had lost over time. They found that up to 58 million trees are near death (see here). If the drought recurs, these trees will die. Another 888 million trees, or about 41,000 square miles of California forests, are drought-stressed. While not as urgently severe, the stress is still dangerous. New tree growth would also be suppressed, leaving room for scrub lands or grasslands to take over, destroying the current ecosystem of plants and animals entirely. That poses a host of new questions for wildlife management and conservation. For example, if the forests go, what does that mean for the bear populations (see here)?
If the forests go, a vital part of California’s water system goes with it. Forest soil acts as a sponge for the freshwater that melts off snowy mountains, holding the water and allowing it to leak out over time. It is this leakage that provides a constant amount of water flowing out the mountain system during the dry summer months. Scrub land, on the other hand, does not hold water. If California loses those 58 million trees, the snowmelt and rainfall would pass through the landscapes they previously occupied without being trapped, becoming susceptible to quick evaporation.
Figure 1: Californian Drought Comparison 2014-2015 (Source: University of California).
The Californian drought. An ecological, a social and a political crisis
This ecological crisis is evolving into a real social and political crisis. What are the policy-makers supposed to do? Water is becoming an increasingly scare good and all sides are lobbying. As water levels in the state reservoirs are falling, officials are cracking down on excess water use (such as lawn watering) and voters passed a water bond on the 2014 ballot to help fund more storage. Some portion of the state’s scarce water resources need to be used to protect wetlands and river habitats (see here). But which portion? Who gets how much?
Poverty stricken towns are running out of water completely. In Central California Valley, thousands are left without running water. The area hardest hit is Tulare County, a rural, agriculture-heavy region in the Central Valley (approximately the size of Connecticut). Some 5.500 people in the county have no access to running water. Most of them live in East Porterville, a small farming community in the Sierra Foothills. This is one of the poorest communities in California: over a third of the population lives below the federal poverty line, 56 percent of adults did not make it through high school. About three quarters of residents are Latino.
Many Tulare homes are not connected to a public water system, either because they are too rural or, in the case of East Porterville, because there was not enough surface water available to serve the community. But until recently, this was not a problem, because the homes have private wells (see here). However, most domestic wells in East Porterville are shallow because water was close to ground level and people are too poor to dig deeper wells (it costs between $ 10.000 and $ 30.000). Today, many of them depend on a free bottled water county delivery service. Each resident is allotted half a gallon of drinking water per day. Some people have been living without running water for over a year. The county set up portable showers. Many rental properties do not have running water and the landlords refuse to pay for wells or domestic water storage tanks.
This means, among other things, that migrant workers are being hit the hardest. The free water programs are open to residents regardless of citizenship, but myths prevent some from using the services. For example, some migrants suspected that the portable showers were an immigration enforcement trap (see here). Aside from all of this, drilling is of course not a solution. Famiglietti, a water scientist at the NASA Jet Propulsion Laboratory, warns that California has only about one year of water supply left in its reservoirs and that the strategic backup supply – groundwater – is rapidly disappearing (see here).
Picture 2: Lake Oroville in California, 2011 and 2014 (Source: Google Images).
Picture 3: Lake Oroville in 2015 (Source Google Images).
The current four-year drought is said to be the worst the area has seen in 1200 years. Currently, approximately 93% of the state is experiencing severe drought or worse. Recent reports showed that farmers use 80 percent of California’s water resources. Severe mistakes have been made in the past – for example farmers grow water-intensive hay in one of the driest regions in the US, the southern Imperial Valley (see here). Farmers, businesses, residents and ecologists fight over what remains. The drought crisis cost California already an estimated $ 2.7 billion and the end is not in sight. The warmer atmosphere this year is demanding roughly 3.5 inches more water off of California’s surface than it was in 1895. That means all of California would need to get 3.5 inches more rainfall each year to meet that demand. But the rainfall is not coming (see here).
Picture 4: The Glen Canyon dam which holds back the Colorado in Arizona. The lake provides water for Nevada, Arizona and California. By 2015, it had been reduced to 42% of its capacity (Source: Newsweek Europe).
California’s value of agricultural output was $46.7 billion in 2013 (see here). California agriculture employed an estimated 348. 900 people in 2013. The agriculture value chain accounts for nearly 3 million jobs.
Figure 2: Importance of agriculture in California for the rest of the country (Source: Mother Jones).
By 2013 – three years into the drought – it was estimated to result in a 6.6 million acre-foot reduction in surface water. The state-wide economic cost of the 2014 drought was estimated at $2.2 billion. The Central Valley, where many of the nation’s fruits and nuts are grown, is the area expected to be most severely affected by net water shortages. As many as 410.000 acres of row and feed crops were not planted in 2014, due to loss of water. The resulting net water shortage of 1.6 million acre-feet was anticipated to cause losses of $810 million in crop revenue and $203 million in dairy and other livestock value, with additional groundwater pumping costing up to $454 million in 2014 (see here). In the meantime, things only got worse. What will happen when the state runs out of the water? No one knows. That is the reality of climate change.