“The love for all living creatures is the most notable attribute of man.” — Charles Darwin

I do hope we all enjoyed celebrating Darwin’s birthday on Friday (Feb. 12), and spent more than just a moment outside enjoying our appreciation for living creatures. It is that appreciation for living creatures (ourselves included) that is at the core of why we have enacted policies aimed to ensure we all have a future on this planet. We have and continue to protect critically important natural areas such as National and State Parks and Monuments, wildlife refuges, and habitat conservation plans. We have controlled our use of pesticides that were otherwise coursing through food webs hitting non-targets up to and including the food that finds itself on our own dinner tables. And, we have managed commercial and recreational hunting and fishing to safeguard that harvests are more sustainable. 

Along the way we have incrementally gained an understanding that, despite its seeming immensity, this planet we call home has limits. The motto of industry and municipalities was once “the solution to pollution is dilution." While at first blush it was so easy and cheap to allow our wastes, our effluents, to be dispersed into the lakes, rivers, oceans and into the air we breathe, we are now increasingly aware of the toll these practices are taking on this planet, and how the more immediate and severe effects are impacting those living creatures and marginalized human communities.

One expression of that impact is climate change. Lots of very smart people were once convinced that the forces that dictate our climate, such as orbital shifts and the angle the earth is tilted toward or away from the sun, were so beyond the power of humans that they ignored other possible sources of climate change. Over a century ago chemists were able to show how molecules comprised of one atom of carbon and two atoms of oxygen, could absorb solar radiation (heat) and hold onto that heat for extended periods, warming our atmosphere and so warming our earth. To a point, the ocean could absorb some of that carbon dioxide, but the oceans have limits and we have reached them. The chemists were right, even though more than a century ago they would not have been able to fathom the levels to which we have added, and continue to add, carbon dioxide into our atmosphere.

Halting and reversing climate change will require the collective and cooperative efforts of every nation. Even if we halted the release of anthropogenic carbon dioxide today, the reabsorption of all that carbon we have sent into the atmosphere so far, back into plants, animals, and soil will take many decades. The immensity of the task of curtailing carbon emissions can easily lead to paralysis. However, there are tasks we can take on as individuals that can lead to “climate adaptation” and “climate resilience." Most of those tasks are aimed at making it easier for people to survive a much warmer earth. But what of those other living creatures?

Some have proposed that rather than refer to our current epoch as the Holocene, we rename it as the Anthropocene, the time of humans. And, because of climate change, they have projected this will be the earth’s next (6^th) great extinction event. The last one was at the Cretaceous-Tertiary boundary, about 66 million years ago when an enormous asteroid (or comet) slammed into the earth just off the coast of the Mexico’s Yucatan peninsula, immediately changing the earth’s climate and atmosphere and causing the extinction of almost everything. The only dinosaurs to escape that extinction event are now called birds. Most of the earth’s five previous major extinction events are thought to be associated with a similar impact from an object originating well beyond this planet. The very first extinction event was different. It was when photosynthesis first evolved, that process in which plants and some bacteria change carbon dioxide into starch and emit oxygen. That influx of oxygen into the atmosphere was toxic to most of the life that had evolved in the anoxic atmosphere up until that point. Only those few species that could thrive in a relatively oxygen-rich atmosphere survived. If this 6^th massive extinction event comes to pass, it too will be the result of the emissions of another organism — us. 

We have had many somewhat smaller extinction events that have been precipitated by climate shifts (shifts resulting from those orbital “wobbles”). Throughout the Pleistocene there were many such shifts, from ice ages to warm interglacial periods and back again and again and again. Mammoths, mastodons, wooly rhinos, camels, horses, giant cave bears, and saber-toothed cats all thrived across North America until about 12-15,000 years ago, but then went extinct, coincident with the retreat of the ice sheets. Except every bird, lizard, rodent and plant that we recognize as our current amazing biodiversity survived. There must be a way, at least for the species we know today, to survive climate change. 

You might imagine the challenge of figuring out how species A or B survived all those ice ages. One important means in that endeavor is a computer tool called Species Distribution Modeling. You start with as many known locations for a species as possible. For each location, with the appropriate database from which to draw from, the computer then calculates the range of soil types, topographies, temperatures, rainfalls, etc., etc., that characterize suitable habitat for that species. Then you ask the computer to chart where those suitable habitats occur across a landscape, and almost like magic you have a map of where a species is likely to find appropriate habitat. Then comes the most interesting step. Using the same model, you now change the climate variables to fit either what it was like during the last ice age, or apropos to our question, what we think it will be like as climate change gets worse. For a mountainous area, the shifts in suitable habitat might be a modest shift up a mountainside. For flat country (think Kansas or Nebraska) it could mean a shift of hundreds or thousands of miles. Sometimes there are overlaps between the current and future distributions. Those areas could be climate refugia, places where species do not have to move to stay within their suitable habitat. Such areas are potentially exceedingly important conservation targets.

Species Distribution Models have the potential to provide powerful insights into the impacts of climate change on our living creatures. However, it is important to remember that they really represent hypotheses, not necessarily reality. We are limited by the types of variables that we can incorporate into the models. It could be that the most important variable explaining why a species occurs where it does is either unknown or unavailable (maybe a specific pollinator, food plant, predator, or symbiotic species plays a critical role). Or at least in the case of animals, perhaps they are capable of behaviorally avoiding climate extremes, something again the models would not be able to “know." This then is the critical role that naturalists can play. These models need to be validated with on-the-ground observational data. In regions that are destined to become unsuitable for a species to survive we could expect reduced recruitment and lower densities. In potential climate refugia we should expect higher recruitment and perhaps higher densities, even with the levels of warming we have experienced so far. These kinds of data are the domains of naturalists. If the existence of a climate refugia can thus be validated, those areas become critical for focusing efforts to control invasive non-native species, for ensuring fire regimes are appropriate for the species therein and focusing other protection efforts. Recently my team was able to model and then validate the existence of climate refugia for Joshua Trees in Joshua Tree National Park. The park managers are now focusing their appropriate fore management in those areas.

It turns out our desert regions are warming twice as fast than almost anywhere on the planet, except the polar regions. Our deserts are, contrary to popular characterizations, also exceptionally rich in biodiversity, so there is the potential for much to lose. What we are finding so far, with the levels of climate change that have occurred so far, is that plants and lizards are shifting incrementally up mountain slopes in areas with the highest levels of aridity (lower elevations, south-facing slopes). It appears that aridity is becoming a better predictor of species shifts than temperature increases alone. Lizards are also much more flexible in their activity times than the models have predicted, being able to shift to earlier into the spring and earlier into the morning to avoid the warmest midday summer temperatures. While species are showing climate stress in the more arid portions of their ranges, in less arid areas they appear to be doing ok, so far. None are racing toward extinction, yet. These insights have been possible by the work of volunteer community scientists, naturalists.  Through their work we are developing a much better picture of the fate of our living creatures that we care so dearly for.

Nullius in verba – take nobody’s word for it. This if the motto of the British Royal Society, the world’s oldest association of scientists and naturalists. In today’s world, it means do not believe what you hear in the news or read on the internet without critically thinking it through – validating or rejecting the hypothesis – through participation as scientists and naturalists.