Reconciliation ecology

Traditional conservation is based on "reservation and restoration"; reservation meaning setting pristine lands aside for the sole purpose of maintaining biodiversity, and restoration meaning returning human impacted ecosystems to their natural state. However, reconciliation ecologists argue that there is too great a proportion of land already impacted by humans for these techniques to succeed.

While it is difficult to measure exactly how much land has been transformed by human use, estimates range from 39 to 50%. This includes agricultural land, pastureland, urban areas, and heavily harvested forest systems.[3] An estimated 50% of arable land is already under cultivation.[4] Land transformation has increased rapidly over the last fifty years, and is likely to continue to increase.[5] Beyond direct transformation of land area, humans have impacted the global biogeochemical cycles, leading to human caused change in even the most remote areas.[6] These include addition of nutrients such nitrogen and phosphorus, acid rain, ocean acidification, redistribution of water resources, and increased carbon dioxide in the atmosphere. Humans have also changed species compositions of many landscapes that they do not dominate directly by introducing new species or harvesting native species. This new assemblage of species has been compared to previous mass extinctions and speciation events caused by formation of land bridges and colliding of continents.[7]

The species-area relationship for a contiguous habitat

The need for reconciliation ecology was derived from patterns of species distribution and diversity. The most relevant of these patterns is the species-area curve which states that a larger geographic area will contain higher species diversity. This relationship has been supported by so large a body of research that some scholars consider it to be an ecological law.[8]

There are two main reasons for the relationship between number of species and area, both of which can be used as an argument for conservation of larger areas. The habitat heterogeneity hypothesis claims that a larger geographic area will have a greater variety of habitat types, and therefore more species adapted to each unique habitat type. Setting aside a small area will not encompass enough habitat variety to contain a large variety of species.[9] The equilibrium hypothesis draws from the theory of island biogeography as described by MacArthur and Wilson.[10] Large areas have large populations, which are less likely to go extinct through stochastic processes. The theory assumes that speciation rates are constant with area, and a lower extinction rate coupled with higher speciation leads to more species.

The species-area relationship has often been applied to conservation, often quantitatively. The simplest and most commonly used formula was first published by Frank W. Preston.[11] The number of species present in a given area increases in relationship to that area with the relationship S = cA^z where S is the number of species, A is the area, and c and z are constants which vary with the system under study. This equation has frequently been used for designing reserve size and placement (see SLOSS debate).[12] The most common version of the equation used in reserve design is the formula for inter-island diversity, which has a z-value between 0.25 and 0.55,[13] meaning protecting 5% of the available habitat will preserve 40% of the species present. However, inter-provincial species area relationships have z-values closer to 1, meaning protecting 5% of habitat will only protect 5% of species diversity.[2]

Taken together, proponents of reconciliation ecology see the species-area relationship and human domination of a large percentage of the earth's area as a sign that we will not be able to set aside enough land to protect all of life's biodiversity. There can be negative effects of setting land aside because it means the remaining land is used more intensely.[4] For example, less land is required for crop production when high levels of inorganic fertilizer is applied, but these chemicals will affect nearby land set aside for natural ecosystems. The direct benefits of land transformation for the growing world population often make it ethically difficult to justify the tradeoff between biodiversity and human use.[14] Reconciled ecosystems are ones in which humans dominate, but natural biodiversity is encouraged to persist within the human landscape. Ideally, this creates a more sustainable socio-ecological system and does not necessitate a trade off between biodiversity and human use.

The life history of the great grey shrike is better understood as a result of focused natural history and reconciliation ecology.

How can understanding of species' natural history aid their effective conservation in human-dominated ecosystems? Humans often conduct activities that allow for the incorporation of other species, whether as a by-product or as a result of a focus on nature.[15] Traditional natural history can only inform how best to do this to a certain degree, because landscapes have been changed so dramatically. However, there is much more to learn through direct study of species' ecology in human-dominated ecosystems, through what is known as focused natural history. Rosenzweig [15] cites four examples: shrikes (Laniidae) thrived in altered landscapes when wooden fence post perches allowed them easy access to pouncing on prey, but inhospitable steel fence posts contributed to their decline. Replacing steel fence posts with wood fence posts reverses the shrikes' decline and allows humans to determine the reasons for the distribution and abundance of shrikes. Additionally, the cirl bunting (Emberiza cirlus) thrived on farms when fields alternated between harvests and hay, but declined where farmers began to plant winter grain crops, natterjack toads (Bufo calamatus) declined when reductions in sheep grazing ceased to alter ponds to their preferred shape and depth, and longleaf pine (Pinus palustris) declined in the Southeastern United States when lack of wildfires prevented its return after timbering.[15][16] Thus, applying focused natural history in human-dominated landscapes can contribute to conservation efforts.

The emerging concept of ecosystem services (coined by the Millennium Ecosystem Assessment in 2005) changed the way ecologists perceived so-called "ordinary species" : as abundant species represent the bulk of biomass and biological processes, even if they don't appear directly threatened their conservation constitutes as a major concern for maintaining these services on which rely both human societies and rarer species.[17] Reconciliation ecology then proposes to take care of such species and to maintain (or restore) ecological processes in human-dominated ecosystems, hence creating ecological corridors and preserving a good functioning of biological cycles.[17]

Increasing wildlife habitat in human-dominated systems not only increases in situ biodiversity, it also aids in conservation of surrounding protected areas by increasing connectivity between habitat patches.[18][19] This may be especially important in agricultural systems where buffers, live fences, and other small habitat areas can serve as stops between major preserves.[20] This concept forms the basis of the subdiscipline countryside biogeography[14] which studies the potential of the matrix between preserves to provide habitat for species moving from preserve to preserve.

Placing importance on native ecosystems and biodiversity within human landscapes increases human exposure to natural areas,[21] which has been shown to increase appreciation of nature. Studies have shown that students who participate in outdoor education programs show a greater understanding of their environment, greater willingness to act in order to save the environment, and even a greater enthusiasm for school and learning.[22][23] Green spaces have also been shown connect urban dwellers of all ages with nature, even when dominated by invasive species.[24] Reconnecting people with nature is especially important for conservation because there is a tendency for people to use the biodiversity present in the landscape they grew up in as a point of comparison for future trends (see Shifting baseline).[25]

The results of reconciliation ecology can also improve human well-being. E. O. Wilson has hypothesized that humans have an innate desire to be close to nature (see Biophilia),[26] and numerous studies have linked natural settings to decreased stress and faster recovery during hospital stays.[27]

While Rosenzweig formalized the concept, humans have been encouraging biodiversity within human landscapes for millennia. In the Trebon Biosphere Reserve of the Czech Republic, a system of human-engineered aquaculture ponds built in the 1500s not only provides a profitable harvest of fish, but also provides habitat for a hugely diverse wetland ecosystem. Many cities in Europe take pride in their local population of storks, which nest on roofs or in church towers that replace the trees they would naturally nest in.[2] There are records of humans maintaining plants in pleasure gardens as early as ancient Mesopotamia, with an especially strong tradition of incorporating gardens into the architecture of human landscapes in China.[28]

Agroforestry in Burkina Faso allows sorghum crop to be grown under native tree species, preserving biodiversity.

Agroforestry provides many examples of reconciliation ecology at work. In tropical agroforestry systems, crops such as coffee or fruit trees are cultivated under a canopy of shade trees, providing habitat for tropical forest species outside of protected areas.[29] For example, shade-grown coffee plantations typically have lower tree diversity than unmanaged forests, however they have much higher tree species diversity and richness than other agricultural methods.[30] Agriculture that mimics nature, encourages natural forest species along with the crops, and also takes pressure off nearby uncultivated forest areas where people are allowed to collect forest products.[29] The understory can also be managed with reconciliation ecology: allowing weeds to grow among crops (minimizing labor and preventing the invasion of noxious weed species) and leaving fallowlands alongside farmed areas can enhance understory plant richness with associated benefits for native insects and birds compared to other agricultural practices.[31]

The oil palm (Elaeis guineensis) provides another example of the potential of reconciliation ecology. It is one of the most important and rapidly expanding tropical crops,[32] so lucrative because it is used in many products throughout the world. Unfortunately, oil-palm agriculture is one of the main drivers of forest conversion in Southeast Asia and is devastating for native biodiversity, perhaps even more so than logging.[33] However, attempts are being made to foster the sustainability of this industry. As a monoculture, oil palm is subject to potentially devastating attacks from insect pests.[32][34] Many companies are attempting an integrated pest management approach which encourages the planting of species that support predators and parasitoids of these insect pests, as well as an active native bird community.[34] Experiments have shown that a functioning bird community, especially at higher densities, can serve to reduce insect herbivory on oil palms, promoting increased crop yields and profits.[34] Thus, oil palm plantation managers can participate in reconciliation ecology by promoting local vegetation that is beneficial to insectivorous birds, including maintaining ground plants that serve as nesting sites, thereby protecting natural communities. Additionally, steps such as maintaining riparian buffer zones or natural forest patches can help to slow the loss of biodiversity within oil palm plantation landscapes.[33] By engaging in these environmentally friendly practices, fewer chemicals and less effort are required to maintain both plantation productivity and ecosystem services.[32][34]

There are many grazing practices that also encourage native biodiversity. In Rosenzweig's book he uses the example of a rancher in Arizona who intentionally deepened his cattle ponds in order to save a population of threatened leopard frogs (Rana chiricahuensis), with no detriment to the use of those tanks for cattle,[2] and a similar situation has occurred with the vulnerable California tiger salamander (Ambystoma californiense) in the Central Valley of California. Research has shown that without cattle grazing, many of the remaining vernal pools would dry too early for the salamanders to complete their life cycle under global climate change predictions.[35] In Central America, a large percentage of pastureland is fenced using live trees which are not only low maintenance for the farmer, but also provide habitat for birds, bats, and invertebrates which cannot persist in open pastureland.[36] Another example from Rosenzweig involves encouraging loggerhead shrikes (Lanius ludovicianus) to populate pastureland by placing perches around the pasture.[2] These are all simple, low-cost ways to encourage biodiversity without negatively impacting the human uses of the landscape.

Green roofs can help maintain species diversity in urban landscapes.

Urban ecology can be included under the umbrella of reconciliation ecology and it tackles biodiversity in cities, the most extreme of human-dominated landscapes. Cities occupy less than 3% of global surface area, but are responsible for a majority of carbon emissions, residential water use, and wood use.[37] Cities also have unique climatic conditions such as the urban heat island effect, which can greatly affect biodiversity.[38] There is a growing trend among city managers to take biodiversity into account when planning city development, especially in rapidly growing cities. Cities often have surprisingly high plant biodiversity due to their normally high degree of habitat heterogeneity and high numbers of gardens and green spaces cultivated to include a large variety of species.[38] However, these species are often not native, and a large part of the total urban biodiversity is usually made up of exotic species.[39]

Because cities are so highly impacted by human activities, restoration to the pristine state is not possible, however there are modifications that can be made to increase habitat without negatively impacting human needs. In urban rivers, addition of large woods and floating islands to provide habitat, modifications to walls and other structures to mimic natural banks, and buffer areas to reduce pollutants can all increase biodiversity without reducing the flood control and water supply services.[40] Urban green spaces can be re-designed to encourage natural ecosystems rather than manicured lawns, as is seen in the National Wildlife Federation’s Backyard Wildlife Habitat program.[41] Peregrine falcons (Falco peregrinus), which were once endangered by pesticide use, are frequently seen nesting in tall urban buildings throughout North America, feeding chiefly on the introduced rock dove.[42] The steep walls of buildings mimic the cliffs peregrines naturally nest in and the rock doves replace the native prey species that were driven out of urban areas.

In Florida, the Florida manatee (Trichechus manatus latirostris) uses warm water discharged from power plants as a refuge when the temperature of the Gulf of Mexico drops.[43] These warm areas replace the warm springs that manatees once naturally used in the winter. These springs have been drained or cut off from open water by human uses. American crocodiles (Crocodylus acutus) have a similar habitat in the cooling canals of the Turkey Point power plant, where an estimated 10% of the total North American population of the species lives.[2]

Wastewater treatment systems have shown potential for reconciliation ecology on numerous occasions. Man-made wetlands designed to remove nitrogen before runoff from agriculture enters the Everglades in Florida are used as breeding sites for a number of birds, including the endangered wood stork (Mycteria americana).[44] Stormwater treatment ponds can provide important breeding habitat for amphibians, especially where natural wetlands have been drained by human development.[45]

Coral reefs have been intensively impacted by human use, including overfishing and mining of the reef itself. One reconciliation approach to this problem is building artificial reefs that not only provide valuable habitat for aquatic species, but also protect nearby islands from storms when the natural structure has been mined away.[46] Even structures as simple as scrap metal and automobiles can be used as habitat, providing added benefits of freeing space in landfills.[47]