Posts Tagged ‘Ecosystems’

A few years ago I wrote a post on niche partitioning among herons and egrets. That post was inspired by watching several species of herons and egrets foraging for food along Putah Creek near Davis, CA, and the resource they were partitioning into niches was food.

Recently, as part of my work at the Sacramento-San Joaquin Delta Conservancy, I encountered another example of niche partitioning by herons and egrets. This time, the resource these birds are partitioning into niches is nesting trees.

One of the grants that I manage at the Delta Conservancy is at the Cosumnes River Preserve and it includes and grove of large Valley Oak trees that many herons, egrets, and cormorants use as a rookery (a rookery is a colony of breeding animals, generally birds). One way that the various species have evolved to utilize the same trees, and yet avoid directly competing with each other, is for each species to utilize a different part of each tree to nest in.

Great Blue Herons typically nest on the very tops of the crowns of trees, Great Egrets typically nest only in the upper one-third of the canopy, Snowy Egrets typically nest in the middle one-third of the canopy, and Black-crowned Night-Herons prefer to nest in the lower one-third of the canopy (see the image below).

Niche partitioning of nesting locations within a tree by heron and egret species

I think this stratifying of nesting locations is amazing! Species have evolved to fill so many different niches, and so many niches can be divided into finer and finer gradations. I wonder if there is really any limit to how many species can evolve, and how complex an ecosystem can develop, in a give location.

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Earth 01

NASA image of Earth.

In 1992, a group of about 1700 scientists signed an open letter to humanity warning of the ecological stressors that human activities were putting on the ecosystems of the earth. In the letter, this international group of scientists outline the various aspects of the natural world that are being pushed to the breaking point.

Now, 15 years later, the situation we find ourselves in has not improved. In fact, it has worsened. The suggestions that those 1700 scientists gave on how to avoid the very foreseeable consequences of humanities consumptive behavior went largely ignored. Another group of scientists are hoping that a second attempt might be more compelling now that many of the predictions produced by climate models are actually appearing. In the U.S., these predictions include the record drought that California and other western U.S. states have recently experienced, the increasing frequency of hurricanes seen off the coast of the southeastern U.S., and the increasing frequency and size of wildfires that have burned


Hurricanes Jose (left), Irma (center), and Maria (right) simultaneously sweeping off the Atlantic Ocean towards North and Central America.

across much of the western U.S. To drive the point home, more then 15,000 scientists have signed a second notice to humanity. In this letter, the authors state that “Soon it will be too late to shift course away from our failing trajectory.”

Too late to shift. Too late to even reduce the impact of the damage of the forces we have already set in motion. We are on a collision course with disaster. The human race is like a person sitting in a car racing towards a stone wall. If the driver sees the wall from far enough away, they can stop the car or turn to avoid a collision all together. If the driver gets closer, there will come a point when a collision becomes certain. But there is still time for that driver to improve the situation. Even if the car is going to crash into the wall, the driver can slam on the breaks to slow the car and possibly only tap the wall. If the driver does not slam on the breaks and only gently taps the breaks, the impact may be significant, but as bad as it could be if the driver does nothing (or steps on the gas!).

Well, humanity has already passed the point where a turn could prevent a collision completely. We saw the wall coming and decided decades ago to keep driving. Now we are in the space where we can slam on the breaks (dramatically reducing CO2 emissions), tap the breaks (somewhat reducing CO2 emissions), do nothing (and continue emitting CO2 at our current levels), or hit the gas (increasing CO2 emissions). But we are not going to be in that space for much longer. In the next few years, we will have committed to the course we are on, and the actions we will have taken will play out across the coming generations.

At present, with the U.S. backing out of the Paris Climate Accord and the current administrations trend toward reducing limits on CO2 and other greenhouse gasses, it is looking more and more like we will hit the wall at the high speed we are currently travelling at, and that massive destruction will be the result.

I think it is very important to remember that the changes in climate that we are seeing across the U.S. and world were predicted to occur. They do not come as a surprise to anyone who has been bothering to pay attention. Now as more predictions are being made about the effects that climate change will have in the future, there should, again, be no surprises if only people would bother to pay attention.


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