Redefining Ecological Restoration

As climate change makes many places uninhabitable, there is a new urgency to restore natural habitats damaged by human activities. 

After a lengthy and contentious battle, the European Union narrowly voted to make a commitment to restore 20% of nature areas on land and sea within their borders.  Farmers were the primary opposition to making this commitment, claiming it would severely reduce their ability to produce sufficient food.  6,000 scientists from several countries disagreed:  “They argued that in the long term, it was climate change and nature degradation that constituted the highest threat, and that the proposed policy would ensure sustainable food production.” (1)

The Biden administration has issued an executive order to conserve 30% of US lands and oceans by 2030.  This 30X30 commitment has been funded by the State of California and is in the early stages of implementation.  In the US, the commitment to “restore” land is often interpreted as a commitment to destroy non-native species with pesticides with the goal of restoring native plants and animals. 

“Restoration” could mean something entirely different and a recently published book, Urban Jungle:  The History and Future of Nature in the City, invites us to redefine restoration in a very different way.  In a nutshell, Urban Jungle proposes to let nature heal itself without a preconceived goal to replicate historical landscapes that aren’t adapted to the climate and the challenging conditions of the urban environment.  Left to its own devices, nature creates novel ecosystems, plant communities that are biodiverse and self-sustaining. 

World War II created a case study of novel ecosystems

When World War II ended in 1945, the Potsdam Agreement determined that Germany would be occupied by the allies that won the war:  United States, United Kingdom, France, and Soviet Union.  The map of post-war Germany (see below) shows the division of Germany among the allies.  The white portion of the map was administered by the Western Allies and the gray portion of the map by the Soviet Union.  Berlin (in red) was deep in Soviet controlled East Germany and was likewise divided into East and West Berlin.  The Soviet Union did whatever it could to isolate West Berlin by restricting access routes to West Berlin and ultimately building a wall around it in 1961.

Berlin was heavily bombed during the war and was largely a pile of rubble at the end of the war.  While other European cities were able to clear the rubble within a few years, West Berlin could not because the Soviets would not let them dispose of rubble outside city limits. 

The physical isolation of West Berlin and the restricted access of the population to the countryside turned West Berlin into an ecological island.  Scientists in West Berlin, with few other opportunities to pursue their interests in botany and ecology, studied and recorded the transition of many tons of building rubble into novel ecosystems populated by whatever plants could find their way there and survive the challenging conditions.  West Berlin was physically isolated from 1945 until the reunification of West and East Germany in 1990, creating a unique opportunity to study natural succession in an urban setting when nature is left alone for nearly 50 years. 

One of the first pioneer plants in West Berlin arrived with the Ukrainian army in the hay brought to feed their horses.  Salsola collina, a tumbleweed, is native to southern Russia and central Asia.  Its arrival was a preview of what was to come, a landscape that would be radically different from the pre-urban landscape.  The plants best adapted to the harsh conditions of the ruined city were hardy non-native species.

Non-native plants that thrived in West Berlin were more tolerant of higher temperatures in an urban setting, where hard surfaces absorb more solar radiation, buildings block the wind, and greater pollution traps heat.  This is known as the heat island effect.  By the 1960s, the temperature in Berlin was on average over 4⁰F higher than the surrounding countryside.

The naturally evolving novel ecosystems in West Berlin were also surprisingly biodiverse.  Where natural succession was allowed to occur over many years, 140 different plant species and 200 insect species were found in the 21^st Century.  In nearby Tiergarten Park, which is carefully maintained as a park, only one-quarter as many insects were found in an area of comparable size.  By the end of the 20^th century, 1,392 naturalized plant species were growing in Berlin, compared to 822 in the 18^th century. 

21st Century equivalent to World War II

Climate change is the 21^st Century equivalent of World War II in its potential to cause death and destruction.  Climate change will create similar requirements to restore environments that are destroyed.  Urban settings will be particularly vulnerable to the consequences of climate change because they are population centers and they are already compromised by urbanization. 

Tidal estuaries and wetlands are one of many ecosystems that are threatened by climate change, as sea-levels rise in a warming climate and intensity and frequency of storms increases flooding.  These threats are greater in urbanized areas because most of our largest cities were built on coastlines and rivers at a time when transportation and shipping was easier by water than by land.

Historically, cities were protected from storms by surrounding marshlands that filtered and cleansed runoff from the land, polluted by human waste. But as cities grew, marshlands were often destroyed to create more land.  In many cases, the landfill was composed of the garbage produced by city-dwellers. 

The closure of urban garbage landfills and the restoration of wetlands to buffer the city from the rising sea and extreme weather events is another opportunity to redefine restoration as a natural process that uses the healing powers of nature.  Urban Jungle uses Fresh Kills Landfill in New York City as an example of restoring nature by leaving it alone.

Fresh Kills was a tidal estuary and marshland on the west side of Staten Island in New York City.  It was opened as a landfill to accept residential garbage in 1948.  By 1986 it had reached peak volume, receiving 26,000 tons of residential garbage per day.  When it was closed in March 2001, the garbage was from 90 to 225 feet tall, weighing 150 million short tons.  It was reopened in September 2001 to accept about one-third of the rubble from the collapse of the World Trade Center on September 11, 2001.  It was the largest garbage landfill in the world when it finally closed.

Fresh Kills Landfill is now in a 30-year process of being restored as a park, renamed Freshkills Park.  The garbage was capped (see below) and methane produced by the decomposing garbage is being captured and used to heat about 22,000 homes on Staten Island. 

The productive wetland ecosystem that was destroyed by the landfill cannot be restored.  Instead, a new ecosystem will slowly emerge on top of the toxic garbage.  The process began by seeding the slopes of garbage with fast-growing plants that were then plowed repeatedly back into the soil to add organic matter.  Then tough native grassland species were planted to provide habitat for initial colonizers, such as insects, small mammals and birds.  Now that basic conditions for life have been established, what happens next is in the hands of nature:  “Freshkills Park will be reclaimed by whatever species are attracted to the foundation of grasses.  Nature will do the bulk of the work, not human beings.  Biodiversity will steadily build as winds and birds bring seeds to the site.  This process of spontaneous successional growth is how nature rebounds from natural disasters such as forest fires, earthquakes, volcanic activity and climate upheaval.  Only in the case of Freshkills Park, the disaster was humanmade.” (2)

Getting off the pesticide treadmill

Allowing nature to heal the places humans have damaged is also an opportunity to get off the pesticide treadmill.  The natural process of succession does not require the use of herbicides to eradicate non-native plants that arrive naturally on the wind, in water currents, and in the stomachs of animals and birds.  When all plants are welcome, there is no need for herbicides and there is more biodiversity that supports more animals and is more resilient as the climate changes in unpredictable ways. 

In a place like Freshkills Park, it would defeat the purpose of turning a toxic landfill into a park public to use herbicides, insecticides, or rodenticides.  New York City banned the use of most pesticides in its public parks in 2021.   

In 2019, France banned the use of glyphosate-based herbicides for non-agricultural use.  The French city of Blois imposed the ban before the national ban was adopted:  “A study published in 2019 found more than 300 species of urban plants sprouting out of the pavements of the French city of Blois, which had recently phased out glyphosate weedkiller.”  (2)

Allowing nature to “manage” our public parks, makes them safer for us and for wildlife as well as more biodiverse than human management that wages a never-ending war on so-called “invasive” plants. There are more bees and bee species in cities than in surrounding countryside because there is more available food in its diverse vegetation:  “Analysis of honey from a bee in Boston, Massachusetts, found it had pollen taken from 411 different species of plants; nearby country honey contained traces from just eighty-two plants.  Cities are islands of biodiversity compared to rural monocultures, with a bigger and more diverse source of nectar even than nature reserves and forests…”  (2)

The takeaway message

Successful restoration of damaged land will take these facts into consideration:

• Many hardy non-native plants are better adapted to challenging urban conditions than native plants: “If native plants can’t hack it in the metropolis, their place should be taken by specialist species drawn from around the world that find niches in the various microclimates of the concrete jungle.”  (2)
• A diverse landscape of native and non-native plants is more resilient in a changing, variable, and unpredictable climate.
• Novel ecosystems created by natural succession are more biodiverse than their historical predecessors.
• When pesticides are used to kill non-native plants, disturbed land is damaged further and is even less likely to support a native landscape.  Killing non-native plants with herbicide also reduces biodiversity. 

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(1) https://www.nytimes.com/2023/07/12/climate/europe-nature-restoration-law.html?searchResultPosition=1

(2) Urban Jungle:  The History and Future of Nature in the City, Ben Wilson, Doubleday, 2023