Ecological Synchrony: Keeping All the Pieces in Place

If you think about nature and how it works, you will likely conclude that everything in your sphere connects in some way. Almost everyone has planted a seed, watched it germinate, grow, mature, maybe fruit, and die. That simple act demonstrates how a system works. The linkages are deep and interconnected from beginning to end.

All life depends on connections. That seed requires environmental inputs - light, water, nutrients. Take away any input and it stretches or challenges the system and may result in failure. With increasing complexity, nature depends on living and non-living inputs. Living soil supports plants, plants support insects, insects support birds - on and on. Some parts of nature are specific, lose one connection and the system fails. Fortunately, most natural systems have redundancies, but as we lose pieces, how it works becomes more fragile. The Leopold quote portrays nature as a very complex system of which we are a part - we depend on it all.

Evidence is building that climate change is affecting how natural systems will or will not continue to function. These changes involve rising temperatures, shifting rainfall amounts, intensity, or seasonality, earlier springs, and any number of observed or measured measures.

There is a tendency to confuse weather and climate. Weather is what we experience day to day, week to week, and season to season. Overtime, weather patterns sum to provide data that represents the climate. While linked, weather and climate are similar, but tell represent very different things.

As climate shifts, natural cycles and processes respond. Because weather is not consistent from year to year, the living parts of natural systems, have the capacity to deal with variation. How nature deals with these shifts is pretty amazing. Nearly all systems have the capacity to flex and absorb change. Individual diversity within species and across species ensures that natural systems tolerate variation and can, over time, recover from individual events; however, if to function requires too much flexing, natural linkages fatigue and break.

Ecological systems have built in synchronization, which suggests there is a natural flow and order. Examples of this are plant germination and leaf color change in the fall. The climate goes through cycles and plants adapt to change and vary their life pattern. The same thing happens with insects, fungi, and amphibians. Probably some of the most obvious and expected examples are specific bird species from overwintering in Central and South American that return to Pennsylvania to breed. If they show up too early, plants and insects may not be ready to support them.

About 100 years ago, C.S. Elton (1924) published a paper that described a now well-known study of ecological synchrony based on the prey and predator relationship between snowshoe hare and lynx. He proposed that this relationship depended on some environmental event that affected hare populations over large geographic regions. That is, something happens that encourages changes in forest conditions which improves conditions that increase hare populations that subsequently over time increase lynx numbers.

Later P.A.P. Moran (1953) evaluated this same data to build a simple mathematical model that basically described how the hare and lynx population changes correlated with weather or other environmental conditions synchronized across separated populations. His model suggested that two widely separated populations should experience synchronized relationships as long as the environmental influence was directionally similar - up or down. This idea has in the past few years come under increased examination as climate change has emerged as a challenge. Unfortunately, only recently have ecologists begun to study how environment is affecting migration and the answers are not simple as there are many variables to understand and consider.

Nonetheless, what happens as climate changes? In the case of species fixed in place, for example trees, they can respond to climate changes; however, there are obviously limits to their ability to adapt, especially if the rate of climate change is faster than their ability to adjust genetically. Ecologists have already started to study and publish papers on tree species migration and some have encouraged human assisted migration - introducing species from warmer areas to places where climate is warming. Temperature is only one variable, what about rainfall, seasonal light levels, soils - some parts of the system may limit adaptability.

Migrating species often have relatively high fidelity to places as they return to the same place year after year. As conditions change locally and across larger regions, local extinctions will occur, especially as preferred plant species, insects, or other needs are no longer available. Sometimes the loss is the result of compounding interactions exacerbated by climate and other human-caused changes such as farming, forest fragmentation, chemicals, non-native plant introduction, loss of insects. In the end, a species change may not be just one thing, it might well be the result of cascading events.

Recently the National Audubon Society released an article about hummingbird migration. Almost anyone who has seen a ruby-throated hummingbird has soft spot for them as they amazingly return across the Gulf of Mexico to breed in the Northeast. Early migrants arrive on our Gulf Coast in early March and start to move north over the next two months. "Climate change is affecting the migration of Ruby-throats, though. As conditions warm on the wintering grounds, data indicate that they leave their winter homes earlier on their way to the Gulf Coast." If these birds leave too early for their trip north, how resilient can they be?

If you have concerns relating to nature and changing climate, what can you do? Of course, you can make individual decisions about life choices. You can become involved in citizen science efforts collecting local data focusing on phenology - the study of cyclic and seasonal natural phenomena. Finding opportunities to help in this regard is as simple as Googling "Citizen Science and Climate Change." Keep your own phenological records of the seasonal change around you. Make comparisons year after year. Track when species are showing up, buds breaking, flowers appearing. It's a useful tool to understand change on your own property.