What is the goal of ecological “restorations?”

In the not-so-distant past, the goal of ecological “restoration” was usually described as the re-creation of an historical landscape that was believed to have been undamaged by humans, presumed to be “in balance” and therefore sustainable after “restoration” without further human management.  In North America, the pre-European landscape is usually selected as the ideal landscape to be replicated, based on the assumption it had not been radically altered by Native Americans.  New knowledge has overturned this model:

• Archaeologists now inform us that human societies have radically altered the environment for thousands of years. The pre-European landscape of North America can no longer be considered a “pristine” landscape.  In fact, nowhere on Earth has escaped anthropogenic change.
• Decades of attempted “restorations” inform us that a continuous gardening effort is required to maintain them.
• Climate change has altered the native ranges of plants and animals and will continue to do so in the foreseeable future. Unless drastic measures are taken to alter the course of climate change, the concept of “native” will become progressively more meaningless.
• Science has rejected the concept of “balance” in nature. Nature is now considered dynamic, constantly changing, often in random, unpredictable ways in response to major ecological events such as earthquakes, wildfires, tsunamis, floods, etc.

Oddly, many invasion biologists accept these new understandings of ecological science without changing their deep commitment to eradicating all non-native plants and animals.  Daniel Simberloff published an article about the current status of the concept of “balance of nature” simultaneously with the publication of his defense of invasion biology.  He described the current thinking about this concept: “…a widespread rejection of the idea of balance of nature by academic ecologists, who focus rather on a dynamic, often chaotic nature buffeted by constant disturbances.”

Invasion biologists have therefore revised their goal for ecological “restorations” to accommodate their new understanding of the dynamic nature of ecosystems.

The revised goal of ecological “restorations”

If the return to an equilibrium state is no longer the goal of ecological “restorations,” what is the new goal?  This is how invasion biologists writing in defense of their discipline described their goal: “…we should seek to reestablish – or emulate, insofar as possible – the historical trajectory of ecosystems, before they were deflected by human activity, and to allow the restored system to continue responding to various environmental changes…” (1)

In this post we will deconstruct this new definition of the goal of ecological “restorations.”  Our first problem with this new definition is that we don’t know the “historical trajectory” of a landscape because it is fundamentally unknowable.  We would have to reconstruct all the events and changes in the environment in the Bay Area in the past 250 years in the imagined absence of any Europeans.  Even if we knew what would have happened without our presence, we cannot then ensure the continuation of that imagined environment because, the fact is, WE ARE HERE AND WE AREN’T GOING AWAY!

Because we cannot reconstruct an imagined environment that has not been “deflected by human activity,” restorationists—who are the practitioners of invasion biology–focus on the one element in the environment of which there is sufficient historical knowledge, i.e., plants.  Most local restoration projects eradicate all non-native plants and trees, usually using herbicides to accomplish that task.  They rarely plant anything after this eradication attempt because they don’t have the resources to do so.  Those few projects that re-plant after non-natives are eradicated usually irrigate the new landscape for several years.  Here is an incomplete list of everything these projects do not do to replicate an historical landscape:

• Soils are not restored for many reasons:
  • We have no way of knowing the composition of soil 250 years ago.
  • Soils have been altered by the plants that have been growing in them and by the herbicides used to kill those plants.
  • Urban soils have high nitrogen levels resulting from exposure to fossil fuel exhaust.
• The atmosphere is not restored:
  • There are much higher levels of ozone and carbon dioxide than there were 250 years ago.
• The climate is not restored:
  • The temperature is higher than it was 250 years ago.
  • The timing of seasons has therefore changed.
  • Precipitation and fog have changed in known and unknown ways.
• The disturbance events that sustained historical landscapes or set them on another evolutionary course are not restored:
  • We cannot set fire to urban landscapes annually without polluting our air and endangering our lives.
  • We cannot allow our creeks and rivers to overflow in urban areas without damaging our properties.
• Most occupants of the historical landscape are not reintroduced:
  • The grazing animals that helped to sustain grassland are gone and cannot be returned to urban landscapes.
  • The top predators such as bears and wolves that kept grazing and other animals in balance with available resources cannot be returned without threatening our safety in an urban setting.
  • Many insects that lived in these historical landscapes are unknown to us and some are extinct.

In other words, destroying plants will not “restore” an historical landscape.  Nor will it return that landscape to its “historical trajectory” even if that trajectory were known or knowable.  Plants live in complex communities in which they are interacting with everything in the environment.  Local “restoration” projects do not “restore” an historical landscape because they do not and cannot change anything other than the plants that occupy the space.  Because most environmental variables have not been altered by these projects, the landscape will quickly return to its unrestored state unless it is intensively gardened.  In that case, the landscape will be continuously “deflected by human activity,” which violates the original goal of invasion biologists.

Misanthropic premise of invasion biology

The revised goal of invasion biology is unattainable because the absence of humans is a prerequisite for its attainment.  We cannot know and we cannot replicate a theoretical historical trajectory for ecosystems in which humans were not present.  And when we modify ecosystems in an attempt to do so, human activities will determine their future trajectory. The premise of invasion biology is that success of ecological “restorations” depends upon the absence of humans. Therefore, invasion biology has no practical application in the real world.   

1. Carolina Murcia, James Aronson, Gustavo Kattan, David Moreno-Mateos, Kingsley Dixon, Daniel Simberloff, “A critique of the ‘novel ecosystem’ concept,”Trends in Ecology and Evolution, October 2014, Vol. 29, No. 10