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Climate and species are a-changin’

8 Oct

This summer was a perfect example of environmental changes. In the northern states, some waterfowl species never migrated south last fall, and this spring’s surveys revealed that some birds migrated north earlier than normal. Conversely, milkweed (Asclepias spp.) emerged one to two weeks early and migrating monarch butterflies arrived two to three weeks late in all the northeastern states. Areas in a few northeastern states were stricken with a historic “100-year or more drought.” On the other hand, many areas in the semi-arid southwest experienced historical devastating floods.

Is this a fluke? Or is this the new norm? Perhaps somewhere in the middle, but more likely these weather and climatic changes are the ‘new normal.’  The events and data support that assessment.*

How do living organisms respond?

Published studies by biologists have been documenting the impact of climate change on the environment, especially species that are adapting and not adapting. We can learn about impacts on organisms  by examining changes in cyclic and seasonal natural phenomena of plants and animals in relation to climate. These seasonal changes and cycles are known as phenology. Noting the times of year that specific plants bloom, or when birds migrate are two examples. Comparing the phenology of many species over a period of time can reveal informative clues on how changes in climate may affect them. Many studies along this model of investigation demonstrate that the living environment is indeed impacted.

United Kingdom researcher Stephen Thackeray(1) and his colleagues analyzed the phenology of a wide range of species. They used 10,003 phenological data sets to determine if and how much species’ phenology have changed over a minimum of 20 years. The analysis revealed that phenology has shifted in unequal rates in different species groups. Thus, climate change leads to disruptions of the phenological match between species, which often impacts ecological relationships.

Another question the researchers asked was how sensitive events in their life cycles are to the two most common variables in climatic change: temperature and precipitation. Both variables have changed in an uneven process over the flow of seasons. How does this impact species relationships? Some periods of the year have warmed faster than others, which may affect two interrelated species with equal temperature sensitivities but at different times. This could shift their phenological events at different rates and cause a mismatch in their relationship.

For example, milkweed plants emerging and flowering much earlier than normal resulted in sub-optimal conditions for the late-arriving monarch butterflies to use the plants for breeding. Additionally, the persistent hot and humid weather in the northeast could impact monarch larva (caterpillar) by either accelerating or arresting development.

trophic-pyramid

Trophic levels

The study authors also discovered a difference of sensitivity to temperature variations at different positions of the food chain (referred to as trophic levels). Species at different levels did not differ in the time of year at which they were sensitive to annual variations in temperature. But they did vary in how sensitive they were.

 

Species in higher levels of the food chain (the secondary consumers) are less sensitive to temperature changes than species at the bottom (the producers and primary consumers). These species are twice as sensitive to temperature changes than upper level species. Secondary consumers are also less sensitive to precipitation variations.

The authors then combined the species sensitivities with a future climate scenarios. They forecast that primary consumers -birds, insects, small mammals, etc- will shift the timing of their phenological events by twice as much as will species at other levels of the food chain. One reason their response varies is because species at different tropic levels respond differently to exactly the same temperature cue. Species respond differently to temperature during various times of the year.

The above example of the milkweed and monarch butterfly mismatch could impact the breeding success and thus population numbers of the butterflies. Both species have different physiological mechanisms that determine their phenological events and use different cues to determine their timing. Although these cues will be correlated to some extent, the cue used by the consumer -in this example, the monarch butterfly- is less reliable than that of the the plant they rely on. This cue unreliability in the consumers may mean that they will evolve with less temperature sensitive phenology than those species at the trophic level they rely on.

Ecologist Marcel Visser (at Netherlands Institute of Ecology) calls attention to moving from conventional two-species interaction research to a more holistic approach: investigating the effects of climatic change on the entire food-web. In a review(2) of the Thackeray, et al. study, Visser additionally proposes that impacts by phenological mismatches could be buffered by other mechanisms in their ecosystems.

To help us understand the consequences of phenological mismatches and thereby form predictions, he proposes questions that should be considered in studying changes in climate changes and relationships:

How are the strengths of the links in a food web affected by phenological mismatches? What happens if the phenology of species at one trophic level shifts more than that of species at another? Does this lead to the loss of some links and the formation of others? Does this destabilize the web? Such analyses would be a stepping stone from studying the phenological shifts of species to understanding the effects of
climate change on ecosystem function.(2)

dscn2300-m

Stink bug preys on larva.

An example for a holistic ecosystem approach is field observations (my own and in the literature) that have suggested that as prolonged temperatures increase, depredation and parasitism of monarch larvae and adults increase. Is this a function of differences in phenology of  monarchs and its predators, or changes in all vegetation and species interactions (a complex of one or more phenological overlapping and mismatches)  in the habitat? Do temperature mismatches in other members of the monarch habitat increase risk or rates of depredation?

One research team suggested that migration of monarch butterflies may have evolved as an adaptation to decrease depredation and parasitism in their breeding habitats. If monarch adults were to delay or ignore cues to migrate because of changing climate, how would that impact their overall population?

Adding to the complexity, climate sensitivity in species is not fixed. Phenological mismatches can lead to selection on the timing of phenological events. Resilience to environmental challenges can alter phenology, but over time can also result in genetic changes to sensitivity, thereby fixing phenological changes. Conventional theory on temperature range sensitivity of monarch adults and larvae states that it quite narrow. However, some observations(3) of their coping mechanisms with prolonged high temperatures in the Pacific Northwest sub-population questions if this sensitivity range is more flexible than conventional thought, or if this could be a developing adaptation.

Some researchers are already investigating genetic changes accompanying phenological adaptations to climate change (e.g. genetic alterations in melanin associated with plumage and physiology in European owls that have adapted to changing ecosystems). Such complex studies must be conducted to forecast the impacts of climate change and phenological responses and ecosystem function.

Research by Thackeray, Visser, and other colleagues demonstrates that long-time series of data are essential for such investigations. They also applaud and encourage professional and citizen scientists to continue collecting and submitting observations to add to the data pool. As Visser commented, “The additional advantage is that observing phenological shifts in, sometimes literally, your own backyard drives the message of global climate change home.”


(1) Thackeray, SJ, et al. “Phenological sensitivity to climate across taxa and trophic levels”. Nature 535, 241–245 (14 July 2016)
(2) Visser, ME. “Interactions of climate change and species”. Nature 535, 236–237 (14 July 2016)
(3) Anecdotal observations by Dr. David James, Washington State University entomologist, in central Washington and myself at Malheur National Wildlife Refuge, eastern Oregon.

* The main difference between weather and climate is time. Weather is the atmospheric local events over a short period of time.  Climate is an average of the weather over much longer time in a region or globally. Sure, we can agree that weather and climate is cyclic, with highs and lows historically up and down. Also, a few episodic variances from the average can be expected.  But climate does not vary as greatly as weather. The trends clearly demonstrate that climate is changing. Modern paleoclimate technologies can now add to the 70-year human records of climatic changes, both which confirm that climate change is a reality. Those changes have accelerated, more than any other equal span of time in historical evidence.

Where water lives

25 Sep

Sitting here in a cafe that squats amidst colorful flowers on the bank of the Selitz River, a warm glow emanates despite the ebb of rain on a metal roof. Light laughter tinkles through the hush of morning people sipping their coffee and reading papers or tapping on their mini-screens like I am now. Outside, underneath large umbrellas, a few people hunch over their cups and table, chatting to each other in soft voices muted by the rain. Conversation alternates between the rare thunder storm here on the Oregon coast and the local events and politics.

A lone fishing boat gently rocks on the dark gray river enveloped by a shade lighter gray sky. Even the trees have a gray cast on this overcast wet morning. Here, on the edge of a river and the edge of an ocean, water also falls from the sky. From a person living the last 17 years where water is so scarce and precious, this abundance almost makes water drip from my eyes.

The moisture here dictates lives, from the moss hanging off trees to the livlihoods of people that call this Home. Growing up in New England where I played in creeks and skated on frozen water, skinnydipped in lakes at midnight and dug new trenches to divert snow water runoff every spring, the arid landscape I moved to challenged my perceptions and perspectives. I learned to do without or with very little water. It became imprinted no matter if water was plentiful or not. Water and its nature taught me much, and it became a respected elder.

What has remained is the magic of water. It doesn’t breathe, cry, or feel pain. Never the less, water can shout, roar, tinkle, and purr. It may be only atoms of hydrogen and oxygen, but it gives us all life. It can carve valleys and populate as bodies. Water can move with force like oceans and rivers, or slowly wander in creeks and be sedentary like lakes. Water can’t vote, plead, or punish. but it can give birth and kill just the same.

Can we justify its abuse, overuse, or contamination because it has no mind, no heart, no voice, and no blood? Is its only merit in monetary value and human recreation? Or might there be an implicit value beyond human assignment?

Perhaps water might be a good teacher of cyclical and dynamic systems, and as a part of all changes on this blue marble in a large universe. It was here long before organized life on this planet. and will remain long after we humans are gone.

Take a walk in the rain and relish its presence. listen to its stories and take care of it as you would a cherished ancestor. Treat it kindly. And go with the flow.

Water Wars

19 Aug

We really have to face up to that long-term history and the ecological reality of living in and building a civilization in a desert region. There is no way to sustain any city in the long run if its water footprint exceeds the natural supply, however many straws we stick into the aquifers. -ecologist Madhusudan Katti

With continuing urban expansion into desert environs, the battle for our most precious resource will escalate. Unfortunately, our typical world view of blaming everything but ourselves, and demanding solutions while ignoring the causal relationships, follows the path of ‘give us more!’. Denying the reality of desert environments and expecting to proceed along ‘business as usual’ will soon face a rather rude awakening. Rightly so.

Ecologist Katti published an excellent commentary addressing this topic on his blog, Reconciliation Ecology. I highly recommend reading it.

Monsoons make us swoon

27 Jul

Rain clouds over the desert in Big Bend.

July and August are monsoon season in the Southwest states. That means the deserts get rain. In most of the SW desert areas, these rains may be the only precipitation that falls during the entire year. Although the average precipitation varies considerably from year to year, and from one location to the next, tracked and recorded patterns provide us with limited ability to forecast a range of expected rainfall. However, in our current era of rapidly changing climate, nothing is certain. Only change.

Historical cycles of drought and abundance of rain are typical of the northern Chihuahuan desert. A severe drought – less than 3″ of rain in a calendar year – were expected on average once every 7-10 years. Conversely, a year or two with abundant rainfall – more than 12″ – may have occured in between drought years. Yet, let us not be too complacent, as some ranchers where in the 1940’s when cattle was overstocked on desert lands during several years of abundant rain. The next years were the driest in recorded history, in this desert and elsewhere: the Dust Bowl years of the 1950’s. Cattle died or were shipped off for pennies, and people left the desert areas to never return.

Predictions of increased temperatures, prolonged drought periods, and reduced precipitation loom over the American Southwest. And we have experienced some of that, such as the drought of 2011 when the southern Big Bend area received only 1-2″ of rain. The ecosystem was hit hard with many losses of plant and animal life, and recovery has been slow. Most people, on the other hand, continue to live and play in the desert, relying on technology to pump water to their taps. But that may be tenuous. Those people that live removed from the infrastructure rely on the same water that the surrounding desert life does: rainfall. And, like camels and succulents, they catch and store rain in containers (albeit, not live tissue like camels and succulents) for measured and conserved use throughout the year.

So we wait. With eagerness, for those winds that blow the rain clouds in. We rejoice and dance outside in the rain. We celebrate. We measure how much rain falls on our homesteads. When the desert smells like rain, no perfume is sweeter. It is the life blood of all desert dwellers.

The Hopi’s have a word for the monsoon clouds: Lakes in the Sky. And indeed they are; floating lakes of water. And we swoon when they dump their precious cargo on and around us.

Obscured sun in monsoon clouds.

Missing the Monsoons

3 Dec

Given the record-breaking drought all across the US southwest, many people living there waited with cautious anticipation for the annual monsoon that delivers 75+% of the region’s annual precipitation.

While it’s unclear when the monsoon will arrive and whether it will deliver on rainfall totals, one thing is completely clear. The region is hanging its hopes on the rains to douse the wildfire flames and quench a thirsty landscape. (from Climas June 2011 report)

The typical monsoon season is over. As Climas has reported,

The 2011 monsoon began and ended with a bang but was lackluster in between. While many regions experienced near-average rainfall, a few periods of widespread and copious rains padded the statistics, particularly in mid-September, turning an otherwise dry summer into an average one…. But after a historically dry winter and a paucity of precipitation forecast for upcoming months, the Southwest will take rainfall in any way it is delivered.

In the Big Bend region of Texas, the rain was little, and a little too late. Our visits there in July and November of 2011 revealed continued drought and its effects on the plant life. Desert areas in the Big Bend National Park, north and east of the park, revealed dead and dying cacti (especially prickly pear) and other drought-tolerant succulents. Overall,  lechuguilla, the indicator species of the Chihuahua Desert, has experienced significant mortality.

Many species of wildlife have also suffered from lack of water and browse. Considering the emaciated condition of the adult doe that perished near our feet last July, fawn mortality and death of adults may have significantly impacted the number of browsing species in the area. Downstream impact on predator species may not be as critical, especially with abundant weak and dying prey.


Except for populated areas with infrastructure that supplies water from aquifers (Alpine, Marfa, etc),  people living off the grid and relying on rainwater harvesting are as eager to see rain as the rest of the desert life. Many have had to resort to hauling water from other water sources.

Meanwhile, the forecast is not heartening. From the October issue of the Climas report (linked above):

La Niña conditions have returned, according to the National Oceanic and Atmospheric Administration (NOAA), and these events historically deliver dry conditions to the Southwest. Current forecasts issued by the International Research Institute for Climate and Society indicates greater than a 50 percent chance that the La Niña event will persist through February.

We daily look hopefully to the sky for rain. And we rejoice when we get even a sprinkling or drizzle, as we did during our November visit.

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