Concepts in Landscape Conservation--An Annotated Bibliography
Biological Integrity
Biological Integrity versus Biological Diversity as Policy Directives. Paul L. Angermeier and James R. Karr. BioScience 44:690-697 (November 1994). The Clean Water Act enunciates the explicit goal of protecting “chemical, physical, and biological integrity.” There is not a specific legislative mandate to protect biological diversity in the U.S, but such protection is a central goal of the Global Biodiversity Protocol endorsed by many nations. Resource policy would be more effective if based on biological integrity. Specific policy shifts include a reliance on preventive rather than reactive management and a focus on landscapes rather than populations. In 1987, the Office of Technology Assessment defined biological diversity to encompass ecosystems, species, genes, and their relative abundance. The focus on different organization levels—taxonomic, genetic, and ecological—is fundamental to the concept. Species diversity alone is not the measure of biodiversity. Elimination of old growth forest, declines in genetically distinct salmonid stocks, and the loss of chemically distinct populations from different portions of a species range represent significant losses of biodiversity, regardless of whether species become extinct.
Biological integrity refers to a system’s wholeness,
including the presence of all appropriate elements and occurrence of all
processes at appropriate rates. Integrity refers to conditions under little or
no influence from human actions; a biota with a high integrity reflects natural
evolutionary and biogeographic processes. Unlike diversity, integrity includes
processes and evolutionary context. Adding exotic species or genes increases
diversity but reduces integrity.
To assess changes in integrity, benchmarks need to be
selected. Functional and evolutionary limits of the native biota provide
objective bases for selecting appropriate integrity benchmarks. For example,
when forest harvest rates exceed regeneration rates, integrity is reduced,
resulting in loss of late-successional communities. When a river is dammed,
integrity is reduced. Use of integrity avoids the pitfall of assuming that
greater diversity or productivity is preferred.
The inadequacy of diversity as a policy directive is perhaps
clearest where humans add elements such as transferred genes, exotic species,
or agricultural landscapes to natural systems. Artificial elements reduce
integrity and should be excluded from evaluations of biodiversity. They rarely
perform life-support services as effectively as native elements and erode
native diversity. We need to protect the processes and products of biogeography
and evolution. These are the processes necessary to generate future diversity.
When ecological restoration is undertaken, efforts should
employ natural ecological processes rather than technological fixes and should
incorporate spatiotemporal scales large enough to maintain the full range of
habitats necessary for the biota to persist under the expected disturbance
regime.
The focus should be shifted from populations and species to
landscapes. The organizational processes and ecological contexts that maintain
populations operate at larger scales than the populations themselves. Safety
net measures are needed to prevent important or unique ecosystems and
landscapes from being destroyed.
Biological Diversity
ECOSYSTEM EARTH. Special Section. Sacha Vignieri and Julia
Fahrenkamp-Uppenbrink. Science
356:258-259 (21 April 2017). Although it is well accepted that Earth consists of
many different ecosystems, it is less well understood that Earth itself is an
ecosystem, dependent on interacting species and consisting of finite resources.
Ecosystem Earth is showing increasing signs of stress. Loss of biodiversity,
environmental degradation, and conflict over resources suggest a state change
is nearing, which could result in collapse of dominant species, development of
alternative biological communities, or collapse of the entire system.
The Interaction
of human population, food production and biodiversity protection. Eileen Crist,
Camilo Mora, and Robert Engelman. Science
356:260-264 (21 April 2017). 10.1126/science.aal2011. Many approaches have been
proposed to meet human food demand while also maintaining biodiversity.
Generally, these involve intensification of food production rather than
expansion, reducing food waste, and changes in diet. These approaches remain
largely idealistic. Yet the scientific community is reticent to discuss global
population size and increase. Slowing and reversing the size of the global
population can be done within a framework of human rights. Protection of the
Earth’s remaining species, genetic heritage, and natural ecosystems needs to be
included as a constraining factor of human development. Extending humanity’s carrying capacity has
usurped resources from other species. To conserve biodiversity, we must protect
large areas from fishing, road building, and intensified agriculture.
Conserving natural ecosystems, species, healthy populations of biota, and
robust ecological and evolutionary processes are needed to ensure a better
future. Addressing the ecological services of the natural world (food, clean
water, climate regulation, crop pollination, recreational space) is an
ecumenical good and an inescapable responsibility.
The intent of sustainable
intensification is laudable, but it is flawed because it (1) accepts the
current massive impact of food production as a roughly acceptable baseline for
supporting humans and (2) it ignores that it is implausible that we can provide
for an additional 2 to 4 billion people without escalating biodiversity
destruction. Human rights policies to empower women would lower fertility
rates. The fertility tide can be turned by making family planning, modern
contraception, and cultural narratives about them a part of everyday life.
Women must achieve equal standing with men. Therefore, education for girls and
women must be ambitiously pursued.
Ecosystem management as a wicked problem. Ruth
DeFries and Harini Nagendra. Science
356:265-270 (21 April 2017). 10.1126/science.aal1950. Ecosystems are
self-regulating systems. As demand for resources increase, management decisions
replace these self-regulating properties. The realization that ecosystems
behave as complex systems, with humans as a component, has upended the notion
that managers can predictably obtain resources by following simple formulas and
exerting top-down control. Ecosystems are inherently dynamic and largely
unpredictable complex systems; therefore, ecosystem management is a “wicked
problem.” Examples of wicked problems are control of infectious disease,
non-point source pollution, fire management at the urban-wildland interface,
and conservation of biodiversity. These types of problems are inherently
resistant to clear definitions and easy predefined solutions. Humans have
increased wickedness by
(1) replacing or supplementing
ecosystem functions such as with pesticides and fertilizers. This does not
mimic the self-regulating properties of ecosystems.
(2) separating in space the
production and consumption of resources. This means locations that experience
the consequences of resource use are disassociated from those where demand
originates, such as with timber harvest.
(3) concern about inequalities in
access to ecosystem resources is becoming more common, particularly where subsistence
communities that depend on local ecosystems are negatively affected by land
acquisition.
Approaches to wicked problems
involve:
(1)
Multisector decision-making where decisions about
single factors do not dominate the multiple services of an ecosystem; for
example, national-level spatial planning and multilevel governance.
(2)
Decision-making across administrative boundaries
which takes place in river basin commissions and large-scale corridor planning
(3)
Adaptive management which recognizes that the
future is unknowable and predictions may have limited reliability. Key features
are monitoring, reassessing initial plans, redefining goals on the basis of new
evidence, social learning, and collaborations.
(4)
Incorporating natural capital and ecosystem
services in markets through payments for ecosystem services, certification
programs, and inclusive wealth accounting. The latter is incorporated into
national accounting systems to complement standard accounting systems.
(5)
Balancing ideologies and political realities of
diverse stakeholders by collaborative planning.
Biodiversity
losses and conservation responses in the Anthropocene. Christopher N. Johnson et al. Science 356:270-275 (21 April 2017). 10.1126/science.aam9317. A
wave of extinctions has followed our species around the earth, reaching back 2
million years when our ancestors adopted the large carnivore niche. This
resulted in the disappearance of sabretoothed cats and long-legged hyenas, and
the reduction of elephants from 12 species to 2. Biodiversity losses can be
halted and even reversed. At least 140 genera of mammals were lost over the
last 100,000 years, a pace that far exceeds background rates. About 23% of the
world’s turtle and tortoise species have disappeared over the past 300,000
years. Prehistoric occupation of the Pacific islands resulted in the loss of
1000 bird species. In New Zealand, 44 of 117 bird species were lost in the last
750 years. These losses are associated with human arrival and are best
explained by the impacts of hunting. This is aided by anthropogenic fires which
change habitat. Extrapolation of trends suggests that the rate of extinction is
about to increase.
Species declines disrupt many
interactions. For example, many woody plants produce large fruits and rely on
large vertebrates for seed dispersal. Large seed size is positively correlated
with wood density and hence high-carbon storage capacity. Loss of mutualistic
partners can therefore lead to tropical forests dominated by fast-growing,
small-seeded plants with lower carbon storage.
In most societies conservation is
not mainstreamed into economic and social planning and human behavior.
Conservation remains largely a discrete sector, which reacts as best it can to
threats generated by other, more powerful sectors such as transport and agriculture.
Conservation is left to do battle with downstream effects. Conservation needs
to be embedded as a primary societal concern, along with prevention of slavery
and child labor. Analyses that include values of ecosystem services along with
market values of products generated after habitat conversion demonstrate large
net economic benefits from biodiversity conservation.
New infrastructure development is a
big threat to biodiversity. There are 334 new hydropower dams planned in the
Amazon basin, and global road-building will add 25 million km of paved roads by
mid-century. Spatial planning should be
used to optimize development versus conservation. In China, the Ecological
Civilization plan prioritizes nationwide land use based on a national zoning of
ecosystem function. Some areas are designated as protected and others with
different levels of development intensity.
Beyond the roots
of human inaction: Fostering collective effort toward ecosystem conservation.
Elise Amel et al. Science 356:275-279 (21 April 2017).
10.1126/science.aal1931. Disruptions of Earth’s ecosystems are a human behavior
problem. Despite widespread awareness and concern, many people continue to
engage in behaviors that further environmental destruction. Some people
increase their anti-environmental behavior as a way to soothe anxiety. Changing
human behavior is hard, and environmental dangers do not arouse the kind of
urgency that motivates individuals to act. Urban industrialized living
compromises an individual’s sense of kinship with nonhuman nature. Feeling
connected to nature leads to more ecologically responsible behavior. We are
especially ill-suited to detect largely invisible and gradually worsening
ecological problems such as climate change or species extinction. These problems
feel psychologically distant. Humans are so disconnected from natural systems
that they do not know what they do not know.
Humans have a psychological need
for safety, security, and to see the world as a stable and just place. Dire
environmental news creates a conflict with these needs. People turn to coping
defenses such as denial or distraction, especially if they have little hope
that action will make a difference.
The most influential need of all is
social connection. Humans are very sensitive to social rejection. The mere
thought of doing something different from what others do or approve of leads to
intense discomfort, embarrassment, or shame. Humans behave according to the
norms of their affinity groups—race, gender, economic status, geography,
politics, religion. Thus, even as climate science data accumulate and consensus
of grave risk grows, concern about climate change has decreased among
conservatives.
This is reinforced because human
brains privilege that which supports their preexisting world view. Any new
information is processed through the filters of personal beliefs, first-hand
experiences, and social identities. Ideas are dismissed or assimilated on the
basis of a quick but biased heuristic of whether they line up with what is already
perceived to be true. It is difficult to escape this bias.
Environmentalism requires
individuals to participate in public dialogue and activism in social
collectives. This is contrary to the way most people behave. Most people
gravitate toward private, individual behavior and avoid uncomfortable public
advocacy and action. It takes courage to
question the dominant worldview that forms the bedrock of cultural norms. There
is the risk of appearing biased, incompetent, rejected, or just facing others
who disagree. People need to know that they are not alone in their beliefs.
They need to know that their individual contribution will make a difference,
and that solutions are possible.
Environmental filtering explains
variation in plant diversity along resource gradients. Etienne Laliberte,
Graham Benjamin L. Turner. Science
345:1602-1605 (26 September 2014). In an Australian site, diversity is determined
by environmental filtering from the regional flora, driven by soil
acidification during long-term pedogenesis. Soil pH explained local plant
species richness. There is no need to invoke factors that might limit resource
competition, such as local resource heterogeneity, resource partitioning,
nutrient stoichiometry, or soil fertility. Increasing soil age was found to
lead to an increase in plant species richness and a decrease in soil pH.
Declining soil pH leads to greater local plant species richness and species
pool sizes. Local plant species richness is greater with larger species pools. The
site was a coastal dune area in Jurien Bay in southwestern Australia (S30ᵒ15’
E115ᵒ0’),
adjacent to the Mount Lesueur area. Vegetation is a kwongan or open Banksia woodland. This is one of the
most floristically diverse regions on Earth, enabling further understanding of
the controls over plant diversity in species-rich ecosystems. A series of dune
sequences dates back 2 million years to the Pleistocene.
Ecosystem function of biodiversity. Yvonne Baskin. BioScience 44:657-660 (November 1994). A workshop sought to pull together what we know about the impact of biodiversity on ecosystem functions. For one important process, net primary productivity, the evidence suggests that above a threshold number of species, increases in species diversity do not improve function. Most natural ecosystems can afford to lose some species without faltering in their production of plant material. Even species that are expendable may help ecosystems endure drought, disease, or global climate change. Therefore, biodiversity helps to hedge bets against uncertainty. Some plants will be drought-resistant enough to compensate for those that are drought-stricken. It could also be that adding more functional types—trees, epiphytes, legumes—will do more to increase productivity that simply adding more species. Even though there are 876 species of trees and shrubs in Asia, 158 in North America, and106 in Europe, productivity is the same. In tropical forests, productivity saturates at 10 to 40 species as long as structural complexity is maintained.
Identifying Extinction Threats. Thomas D. Sisk, Alan E. Launer, Kathy R. Switky, and Paul R. Ehrlich. BioScience 44:592-604 (October 1994). A new tool for analyzing anthropogenic threats to biodiversity is based on geographic patterns in species distributions, species habitat use, forest loss, and human demographic trends. Countries that support high levels of species endemism or diversity and that have a history of rapid forest destruction are identified. The rate at which habitats are being lost is probably more important for determining risks of extinction than the present commonness or rarity of the species living in them. We used two species databases, mammals and butterflies, a forest-loss database, and a human demography database. The human demography database is a surrogate for habitat loss other than forests—grassland plowing, overgrazing, wetland drainage, damming of streams, toxification of soils and waters, hunting, and introductions of exotic organisms. Key countries for the conservation of biodiversity globally are China, India, Columbia, Ecuador, Madagascar, and Philippines. Other countries of global concern are Taiwan, Thailand, Vietnam, and Costa Rica.
Understanding and Saving Big Predators. Matthew E. Gompper. Science 345:1460 (19 September 2014). 10.1126/science.1256065. Review of The Carnivore Way: Coexisting with and Conserving North America’s Predators. Cristina Eisenberg. Island Press, 2014. Studying large carnivores is one of the few realms in which one gains insights into the ecological importance of not just a species or a population but the actual individual animal. Because of its size, the presence of an individual carnivorous animal is important-through its land use, or shifts in its behavior, the individual animal can have a drastic effect on the community. The return of wolves can have drastic effects on the vegetation. Wary prey browse less in one place. Large predators increase biodiversity and create more resilient ecosystems. This book focuses on six species in the mountain west—grizzly, wolf, wolverine, lynx, jaguar, and cougar. The next frontier in carnivore conservation will be the Great Plains and eastern deciduous forests.
Defaunation in the Anthropocene. Rodolfo Dirzo et al. Science 345:401-406 (25 July 2014). Doi: 10.1126/science.1251817. Human impacts on animal biodiversity are an under-recognized form of global change. Both vertebrate and invertebrate populations are plummeting, with impacts cascading onto ecosystem functioning and human well-being. This human mass extinction is the sixth great extinction of earth history. Defaunation needs to be recognized at the same sense as deforestation. Defaunation can occur even in protected habitats. About 16 to 33 percent of all vertebrates are threatened or endangered, and invertebrate declines are at least as severe. Butterfly and moth declines are in the range of 35 percent, with other invertebrates likely more. Vertebrate extinction, rare, and endangered species is focused on larger body sizes. Climate change is likely to soon compete with habitat loss as the most important driver of defaunation. Major impact categories:
· Pollination. Pollinators are declining in abundance globally. Declines in bird pollinators in New Zealand has reduced seed production and population regeneration. Insect pollination is needed for 75 percent of the world’s food crops.
· Seed dispersal through loss of flying foxes.
· Litter respiration and decomposition through loss of seabirds
· Carrion removal through loss of vultures.
· Herbivory through loss of large mammals.
· Trampling of seedlings through loss of mammals.
· Pest control. Declines in small vertebrates affect herbivore abundance, plant damage, and plant biomass. Losses from arthropod pests increase without predators.
· Nutrient cycling. Declines in mobile species that move nutrients long distances greatly affect patterns of nutrient distribution and cycling. Loss of dung beetles affects dung removal. Pleistocene extinctions are thought to have changed influx of phosphorus in the Amazon by 98%, with implications persisting today. P is a limiting nutrient. Carbon cycling is affected by loss of nematodes
· Water quality. Global declines in amphibian populations increase algae and fine detritus biomass, reduce nitrogen uptake, and greatly reduce whole-stream respiration. Large animals stir up the water and prevent formation of anoxic zones.
· Soil erosion through loss of prairie dogs.
· Human health. Between 23 and 36% of all birds, mammals, and amphibians used for food or medicine are threatened with extinction. Loss of wild food sources with increase anemia in human populations.
· Evolution. Changing body-size distribution will affect evolutionary patterns. Changes in pollinators will cause rapid evolution in plant mating systems and seed morphology.
Defaunation will combine to push us to global-scale tipping points. Immediate mitigation of animal overexploitation and land-use change are needed. Anthropocene defaunation is a characteristic of the planet’s sixth mass extinction and a driver of fundamental global transformations in ecosystem functioning.
Reversing Defaunation: Restoring Species in a Changing World. Philip J. Seddon et al. Science 345:406-412 (25 July 2014). Doi: 10.1126/science.1251818. Conservation translocations seek to restore populations outside their indigenous range or to introduce ecological replacements for extinct forms. There is a bias towards birds and mammals in this effort, and there was initially a very low success rate. It needs to be recognized that restoration to a completely natural state is unrealistic, especially given climate change. Releases inside the indigenous range are reinforcements, such as the black stilt, or reintroductions, such as Hamilton’s frog. Outside the indigenous range, they are assisted colonizations, e.g., Tasmanian devil. Translocations with the objective of restoring ecosystem function are a component of rewilding (gray wolf). If an ecological function has been lost, such as dispersal of large-seeded plants by giant tortoises, a substitute species may make up for the extinct one (ecological replacement). In many cases, the appropriate ecological replacement would not be an endangered species. Ecological replacement is a departure from the single-species focus. Its most important application has been on islands where herbivory and seed dispersal functions can be restored by large frugivores. This has worked when Aldabra giant tortoises have been introduced to Mauritian offshore islands (Round Island) to replace an extinct tortoise. Seed dispersal has resumed, and seed germination has improved. Rewilding has been an abused term, but it needs to mean creating an area where predator-prey interactions are managed within landscapes shared by humans and wildlife.
Eating Ecosystems. Justin S. Brashares and Kaitlyn M.
Gaynor. Science 356:136-137 (14 April
2017). 10.1126/science.aan0499. Hunting reshapes entire ecosystems and, in some
cases, human societies. It changes food web interactions, enables disease
transmission to humans, and funds militias. During the Pleistocene, hunting
contributed to the extinction of more than 100 genera of large-bodied mammals,
including giant bison, mammoth, tapir, and ground sloth. However, this pales in
comparison with current ecosystem damage. Wildlife harvest presents a major
threat to animal persistence throughout the tropics. Wild meat consumption is
driven by food insecurity and limited access to alternative protein sources,
and is also linked to poverty, livelihood opportunities, and market dynamics.
For wealthier people, there is the cultural importance of hunting and preferences
for wild meat. The empty forests created
are compromised ecosystems, with weakened food webs and impaired ecosystem
functioning, altering populations of plants, competitors, prey, and predators.
There will be long-term changes in hydrology, fire, nutrient cycling, pest and
pollination dynamics, and carbon flux. These compromise the sustainability of
agriculture.
Quantifying hunting-induced defaunation. Science 356:150 (14 April 2017). A
large-scale meta-analysis of hunting trends and impacts across the tropics
suggests that all hunting has worrying impacts. Sustainable subsistence hunting
must be implemented soon to prevent further, rapid defaunation.
The impact of hunting on tropical mammal and bird
populations. A. Benitez-Lopez et al. Science 356:180-183 (14 April 2017).
10.1126/science.aaj1891. A review of 176 studies indicates that bird and mammal
abundances declined by 58% for birds and 83% for mammals in hunted areas.
Indeed, the abundance of wildlife in natural ecosystems is more closely related
to patterns of hunting than to factors such as forest type, habitat area, or
habitat protection status. There is also evidence of size-differential mammal
defaunation for frugivores, carnivores, herbivores, and insectivores. Protected
areas help but even in these areas overhunting is occurring. Gazettement of
protected areas must be accompanied with improved reserve management and law
enforcement. Large vertebrates are depleted near settlements and roads.
Genetic Engineering
Ready to Go to Market? Philip J. Regal. BioScience 44:706-708 (November 1994). Review of Perils Amidst the Promise: Ecological Risks of Transgenic Crops in a Global Market. Jane Rissler and Margaret Mellon. Union of Concerned Scientists, Washington, 1993. There are two accounts of scientific consensus in the genetic engineering narrative. In the M account, there is a desire to project the impression that there is a scientific consensus that genetic engineering is basically no different from conventional breeding and can present no new threats to the environment. In the E account, genetic engineering is not magic, and will not unexpectedly produce godzillas. In this account, most genetically engineered organisms will be ecologically safe because they have been built by introducing non-adaptation-enhancing traits into ecologically incompetent hosts. Yet in this second account, there will be risks when truly novel adaptiveness is engineered into competent hosts. The E account is why ecologists must be urgently consulted. So far, the regulatory programs of EPA and USDA seem to have discouraged the more reckless projects. However, as genetic engineering becomes more widespread, biological novelties will be scattered to the corners of the earth. This book is a good point of entry into biotechnology environmental issues.
Framing
Whose Conservation? Georgina M.
Mace. Science 345:1558-1560 (26
September 2014). 10.1126/science.1254704. There have been four phases in the
framing of conservation by conservation biologists. During the 1960s and 1970s,
the ‘nature for itself’ frame prioritized wilderness and intact habitats. In
the 1980s and 1990s, the ‘nature despite people’ frame focused on threats to
species and on strategies to reverse losses. Ideas concerning minimum viable
population sizes and sustainable harvesting levels stem from this period.
During the 2000s, conservation moved away from species and toward ecosystems as
a focus, with the goal of providing sustainable benefits in the form of
ecosystem services. This is the ‘nature for people’ frame. Since 2010, this has
modified to recognize the two-way, dynamic relationship between people and
nature. This ‘people and nature’ thinking emphasizes the importance of cultural
structures and institutions for developing sustainable and resilient
interactions between human societies and the natural environment. The Nature
Conservancy recently moved away from a focus on preservation toward exploiting
opportunities for conservation outcomes that businesses will invest in for
their own benefit. The problem with the more recent framings is that there are
not good metrics, and an inability to put ecosystem values in economic terms
will result in them being evaluated as having no value.
Tipping Points
On
the Edge. Gabriel Popkin. Science
345:1552-1554 (26 September 2014). Ecologist Martin Scheffer was one of the
first to recognize tipping points in lakes in the Netherlands. The lakes had
two stable states and quickly shifted as a result of a small external nudge. A
classic paper was published in 1993 in Trends in Ecology and Evolution. Today
Scheffer tries to identify tipping points in tropical forests, global climate,
and gut microbes. He is the chief networker for tipping point researchers. The
Resilience Alliance is an eclectic confederation of scientists who study what
makes some systems stable in the face of change. A 2001 Nature paper aimed to
bring the concept of ecological tipping points into the mainstream and drew on
studies of lakes, coral reefs, forests, deserts, and oceans. He conceived the
South American Institute for Resilience and Sustainability Studies, now under
construction in Uruguay.
Mapping Human Impacts on the Global Biosphere. Marc L.
Imhoff. BioScience 44: 598 and front
cover (October 1994). Attempts to identify areas of broad and intense
perturbation of native habitats should be an integral part of any effort to
identify priority areas for conservation. Maps were developed from high
resolution data bases (1⁰ latitude by 1⁰ longitude on a global grid. A grid
square was considered agriculture if 50 % or more was under cultivation.
Ecosystem Services
Pursuit of the common good. Partha Dasgupta and Veerabhadran Ramanathan. Science 345:1457-1458 (19 September 2014). 10.1126/science.1259406. The rise of market fundamentalism and the drive for growth in profits and gross domestic product have encouraged behavior that is at odds with the pursuit of the common good. Unsustainable consumption, population pressure, poverty, and environmental degradation are linked, but this is not appreciated by development economists or national governments who permit GDP growth to trump environmental protection. A Vatican workshop was convened to reflect on issues at the nexus of poverty, population, consumption, and environment. Economic growth discussions need to include natural capital inventories. This would provide an indication of true wealth. Anthropogenic climate change raises questions about the responsibilities we have to one another and to nature, since the majority of emissions are by 1 billion and the other 6 billion suffer the consequences. Access to energy by the poor is also needed, since much of the use of firewood, dung, and crop residues contributes to climate change.
Using ecological thresholds to evaluate the costs and benefits of set-asides in a biodiversity hotspot. Christina Banks-Leite et al. Science 345:1041-1045 (29 August 2014). 10.1126/science.1255768. People will benefit more from the ecological functions of biodiversity if these functions occur across the biome, not just inside protected areas. Payment for ecosystem services (PES) projects are being developed across the globe to reimburse private landowners. To do this, you must first estimate the minimum amount of habitat required to maintain biodiversity. If too much land is set aside, it is costly, but if too little is in play, then ecological gains are minor. We used the Atlantic Forest in the state of Sao Paulo for analysis. For the Atlantic Forest, data from a field study capturing animals suggests that the number is 28.5 percent forest cover. Communities above this threshold tend to be dominated by forest specialists, and communities below it by disturbance specialists. We assessed the ecological benefits and economic costs of paying landowners to set aside private land for restoration in the Brazilian Atlantic Forest. An annual investment equivalent to 6.5% of what Brazil spends on agricultural subsidies would revert species composition and ecological functions across farmlands to levels found inside protected areas.
Land-Use Change
The Global Impact of Land-use Change. D.S. Ojima, K.A.
Galvin and B.L. Turner II. BioScience 44:300-304 (May 1994). Agroecosystems
most vulnerable to future climate are those that are near the limits of water
nutrient availability and temperature constraints or that have pests or
diseases controlled by climate. Land use modifies global changes because land
use affects community composition, net carbon fluxes, water and energy fluxes,
and biogenic trace gas exchange. Fragmentation often has far-reaching effects. Half
of the land surface is cropland or pastures and half of the cultivated areas
have been added in the last 100 years. This has contributed to increases in
carbon dioxide.
The Worldwide Extent of Land-use Change. R.A. Houghton.
BioScience 44:305-313 (May 1994). In the last few decades the effects have
become global rather than local, and contribute to climate through increasing
emissions of greenhouse gases. This type of change affects all regions, whether
or not the region contributed to the change. There is an element of choice in
what one does with one’s land, but not in what happens to the earth’s climate.
Only one-half of the area of tropical forest lost each year actually expands
the area in productive agriculture. The other half replaces worn-out, abandoned
lands. This is then abandoned after a few years. Making agriculture sustainable
may be twice as effective in halting deforestation as is increasing yields.
Restoration
Living by the lessons of the planet. Jonathan Foley. Science 356:251-252 (21 April 2017). 10.1126/science.aal4863.
The classic Malthusian view of population growth overlooked changes in
technology, food production, and reproductive behavior that occur as nations
develop. Nevertheless, as population grows to 11 billion by the end of the 21st
century, the problems caused by population growth, increasing wealth,
technological advancement, rapidly increasing natural resource exploitation,
ongoing global environmental degradation, and increasing human vulnerability to
environmental disasters are a major concern. The underlying dynamics described
in The Limits to Growth (1972) have
held up well. Our planet has fundamental limits imposed by physics and biology.
Activities that go beyond these fundamental limits might last for a while but
are not sustainable.
The concept of planetary boundaries considers the entire
Earth system and asks whether human activities have pushed the planet’s
environmental systems outside the realm of geologic experience during the
Holocene epoch (last 10,000 years). This includes the climate, land resources,
ecosystems and biodiversity, fresh water, ocean chemistry, atmospheric
chemistry, and biogeochemical cycles. Of this list, humans have clearly pushed
climate (increased greenhouse gases by 50% and acidified the ocean), land (converted
40% of the Earth’s surface to agriculture), biodiversity (much of it
obliterated), and biogeochemical flows (fertilizers nitrogen and phosphorus
have radically alternated natural cycles) past the experience of the Holocene. We
have pushed on to a new epoch, the Anthropocene.
Ideas emerging in the emerging circular economy framework,
such as the “natural step” and the “ecological footprint” are useful. Natural
ecological systems do not consume resources faster than they are regenerated;
they do not produce wastes faster than they are assimilated; and are highly
diverse, making them resilient. These three ideas can help us reinvent our
food, water, and energy systems.
Coevolution of Agroecosystems and Weed
Management. C.M. Ghersa et al. BioScience 44(2):85-94 (February 1994). Humans
create the necessary habitats for both crops and weeds. Crop and weed species
often share taxa; they can serve as gene pools for hybridization and
introgression. Many weeds have recently evolved from diverse parentage under
agricultural pressure. The native origin cannot be determined. The rapid gene
flow among weeds and crops raises an important and practical issue with the
imminent wide-scale release of engineered crop traits. Assessments of the risks
associated with resistant and/or engineered genes must recognize the
possibility that human interactions affect evolutionary processes in
agroecosystems. Today’s weeds are more persistent than historical weed floras
because they have demographic traits that have evolved and resistance to
herbicides. The evolution of weeds may have produced changes in the way that
weeds directly affect crop yields. Also, evolution may have created weeds that
are more difficult to eradicate and control. Neither question has been
addressed experimentally. Despite the enormous effort to control weeds,
relative and absolute abundance of the weed flora increased steadily from 1900
to 1980. Replacing herbicides with cultural practices is not enough. To achieve
healthy coevolution between agroecosystems and weed management requires the
recognition by social institutions that this coevolution is a desirable
process. The key in healthy coevolution is to find ways to minimize the use of
energy and maximize the use of information when designing weed management
strategies.
Repairing
Ecosystems. William E. Stutz. Science 345:388 (25 July 2014). Review of Our
Once and Future Planet: Restoring the World in the Climate Change Century.
Paddy Woodworth. University of Chicago Press, 2013. The book focuses on
restoration ecology, or the regeneration and repair of degraded ecosystems.
There are country-wide efforts to remove invasive trees in South Africa, the
transformation of ill-fated farmland to native bush in Western Australia, and
the restoration of bog lands in Ireland. The biggest debate in this field is
about whether we should seek to recover historical reference ecosystems or
whether this is doomed by climate change. Instead, we must embrace novel
ecosystems.
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