Food webs entangle humans in complex relationships with animals, crops and the environment

Reconstructed food webs from the Ancestral Puebloan southwestern United States show the complexity and interconnectedness of humans, other animals, crops and the environment, in an area of uncertain climate and resources, according to researchers, who think climate change and human decisions then, may shed light on future human choices.

Square Tower House in Mesa Verde National Park [Credit: Nate Crabtree]

"As southwestern archaeologists, we know that Ancestral Puebloan people were intrinsically connected to the environment," said Stefani Crabtree, postdoctoral fellow in human behavioral ecology in the Department of Anthropology, Penn State. "But, most food webs have omitted humans."

Traditionally, food webs, while they map the interaction of all the animals and plants in an area, usually do not emphasize the human component. Crabtree and colleagues created a digital food web that captures all categories of consumers and consumed, can be defined for specific time periods and can also represent food webs after major food sources or predators disappear from the area. If an area suddenly becomes devoid of deer or humans or corn, for example, a food web of that situation can show where predators went to find prey, or which prey thrived for lack of a predator.

These knockout food webs -- webs missing a specific predator or prey -- show the changes and pressures on the food sources substituted for the missing ones, or the changes that occur when pressure is removed by removing a major consumer. The researchers report the results of their study in the Journal of Archaeological Science.

"When people show up in the area around A.D. 600 they bring corn," said Crabtree. "It takes a while for critters to get used to it, but eventually, everything that eats vegetation, eats corn and prefers it."

Humans bringing corn into an area is a major disruption of the existing food web. Planting corn means clearing fields to displace whatever plants and animals were there, creating a high-energy plant source of food and switching plant eaters to the preferred higher-calorie food source.

In the American Southwest, the Ancestral Puebloan people eventually preyed on their deer population enough so that they deer were no longer a reliable source of food. To compensate for this, they began to domesticate turkeys for food. Turkeys need to be fed corn if they are captive and that competes with corn for human consumption. At this time, corn made up 70 to 80 percent of Ancestral Puebloans' food and so feeding turkeys altered the food web.

A sample food web with red nodes representing primary producers, orange nodes primary consumers, yellow-orange 
nodes omnivores, true-yellow nodes are true carnivores. This draft food web was created with the program 
Network3D from foodwebs.org [Credit: Stefani Crabtree, Penn State]

To create the food web, the team identified all the common, noninvasive species in the area. They then added species that were found in archaeological sites, but were absent from the modern lists. In some food webs, components are identified by their function, so all humming birds are considered flying pollinators, but in this case each type of humming bird received its own place in the web, linked to what it ate and what, if anything, ate it. This produced a very complicated web, but supplied exceptional redundancy.

"In the insect world it is harder to get at the data," said Crabtree. "We have not been able to get at good databases so we aggregate at the functional level -- pollinators or bloodsuckers for example."

The exception to individual web entries then are invertebrates -- insects, spiders, snails, etc. -- that were classified by their function. Invertebrates are organized to the level of order and then grouped by function. With insects, for example, the researchers would group butterflies and moths that pollinated and sipped nectar, together in one group.

The overall food web had 334 nodes representing species or order-level functional groups with 11,344 links between predator and prey.

The researchers realize that there are differences in the environment between now and the Ancestral Puebloan period, but many things, such as pinon-juniper woodlands and sage flats are the same. Enough similarity exists for this approach to work.

The team did not produce just one overall food web, but also food webs corresponding to three archaeological locations and three time periods of Ancestral Pueblo occupation in the area -- Grass Mesa Pueblo for Pueblo I, Albert Porter Pueblo for Pueblo II and Sand Canyon Pueblo for Pueblo III. They began with using archaeological assemblages from these sites incorporating all human prey and all human predators into the food web. Then they included the prey of the primary prey of humans and then predators of these human-prey species. Prey, in this case, includes animals, insects and plants.

A coyote preying on an entire clutch of baby rabbits in Boulder County, CO. [Credit: Mindy Wilkinson]

When creating knockout food webs, the researchers included only those species that were found in reasonable quantities in the archaeological assemblages at those times.

"Knockout food webs are one of the best ways to understand how people interact with the environment," said Crabtree. "Because we can remove something, predator or prey, and see what would happen."

When major changes in climate variables such as drought, heat and lack of snowpack are factored in, the balance in the food web may become unstable. When food becomes scarce, most mobile creatures, animals and insects move to another location. During the time of the Ancestral Puebloans, this was possible and eventually, these people moved to the area of the Rio Grande in New Mexico and other places in New Mexico and Arizona.

"We didn't have a long-term plan during the 600 years of Ancestral Pueblo habitation in the Mesa Verde region," said Crabtree. "We don't have a long-term plan today either. We don't even have a four-year plan. Some people are pushing us to look closely at climate change."

In the past, people migrated, said Crabtree. Unless we figure out better strategies, where are we going to migrate out to? We do not have a place to go, she said.

What people plant and eat has a great effect on the environment and on ecosystems. In the end, those choices will impact human survival, according to the researchers.

This work is part of a collaboration of researchers creating resolved food webs from a variety of places. Crabtree believes that she can compare this project to others that include humans in other geographical areas to help understand ecosystems with humans in them.

Author: A'ndrea Elyse Messer | Source: Penn State University [April 10, 2017]

byUnknown

in Americas, Archaeology, Climate Change, Ecosystems, Environment, North America, USA, Wildlife

April 10, 2017

Food webs entangle humans in complex relationships with animals, crops and the environment

Reconstructed food webs from the Ancestral Puebloan southwestern United States show the complexity and interconnectedness of humans, other a...

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Putting a price tag on biodiversity

Talk to just about any biologist long enough and the conversation will steer toward the benefits of biodiversity. Although the ecological benefits of biodiversity are well documented, those benefits have rarely been expressed in dollars and cents. A team of economists and ecologists, including University of Illinois professor of environmental economics Amy Ando, has developed one of the first models to assign a dollar value to the loss or gain of species in an ecosystem. This new work offers an economic argument for preserving biodiversity.

The Cedar Creek Biodiversity Experiment: Each plot has 1, 2, 4, 8 or 16 different species of perennial prairie plants. 
Planted in 1994, this long-term experiment has shown that greater biodiversity leads to greater ecosystem
 productivity and carbon storage [Credit: G. David Tilman]

"Biodiversity has value in its own right, as people marvel at the beauty and variety of the many faces of nature," says Ando. "But those intrinsic values can be hard to quantify. In this study, we pinned down the monetary value of one particular practical service that biodiversity provides to people: carbon storage." The research team was led by Bruce Hungate, director of the Center for Ecosystem Science and Society at Northern Arizona University. The findings are published in Science Advances.

To build the model, the researchers first had to identify some measurable service of biodiversity that society has priced. Although biodiversity provides many valuable services, concern about climate change has led economists to put a dollar value on the abatement of climate-warming carbon emissions (ranging between roughly $40 and $400 per metric ton). And now there's a $175 billion global carbon market that pays for activities that remove carbon from the atmosphere.

Biodiversity could enter the game through a 4-billion-year-old form of carbon storage that plants provide: photosynthesis. Plants absorb carbon dioxide for energy and growth, storing the carbon in their leaves, stems, and roots, and later transferring it to the soil through decay. The key is to link biodiversity and carbon storage in a quantitative way. So researchers asked: Will changing the number of plant species in an ecosystem affect the amount of carbon it stores over time?

The National Socio-Environmental Synthesis Center (SESYNC) convened the team of scientists, which analyzed data from two long-term experiments in Minnesota grasslands that measured how plant and soil carbon changed with the number of plant species in a plot. Modeling results over 50 years, they estimated the "marginal" increase in carbon storage, or how much additional carbon is stored for every species added to the mix.

Each additional species in a grassland plot increased the plot's overall carbon storage, on average. One reason for this gain may be that new species can fill new niches, yielding more overall growth.

With more species came diminishing returns in cumulative carbon storage. A change from five to six species stored almost 10 times more carbon than a change from 15 to 16 species, showing that the biggest benefit came from adding species to the least diverse plots.

At small scales, about 2.47 acres, going from one to two plant species over a 50-year time period would store an additional 9.1 metric tons of carbon, potentially saving $804 per 2.47 acres based on a mid-range estimate ($137 per metric ton) of the social cost of carbon. At larger scales, cost savings could hypothetically be significant. For example, adding just one species to the approximately 29.5 million acres of cultivated lands restored to grasslands by USDA's Conservation Reserve Program could save over $700 million. The biggest cost savings come from restoring the most degraded, species-poor lands.

These numbers underestimate the total value of increased biodiversity because biodiversity confers economic value in many ways beyond storing carbon. "Biodiversity means products like wood, food, and fuel, and services like recreation, water purification, and flood protection, all of which could be quantified using our approach," says Hungate. "Money is a language that speaks, and showing the economic value of biodiversity underscores the importance of conservation and the policies that support it."

Although the value of biodiversity is more complex than just one economic measure, this new research takes a bold step toward understanding the value of nature.

Author: Debra Levey Larson | Source: University of Illinois College of Agricultural, Consumer and Environmental Sciences (ACES) [April 06, 2017]

byUnknown

in Biodiversity, Ecosystems, Environment, Natural Heritage

April 06, 2017

Putting a price tag on biodiversity

Talk to just about any biologist long enough and the conversation will steer toward the benefits of biodiversity. Although the ecological be...

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First world survey finds 9,600 tree species risk extinction

The first ever global database of trees on Wednesday revealed that 9,600 tree species are threatened with extinction and identified a total of 60,065 in existence.

Brazil is the country with the most diverse tree population, with 8,715 species, according to the Botanic Gardens 
Conservation International (BGCI) group [Credit: AFP]

Brazil is the country with the most diverse tree population, with 8,715 species, according to the Botanic Gardens Conservation International (BGCI) group.

It also has the largest number of tree species—4,333—that only exist there.

In total 58 percent of trees are so-called single country endemics, with 2,991 species only found in Madagascar and 2,584 only found in Australia.

After Brazil, Colombia is the second most diverse country, with 5,776 different tree species, followed by Indonesia, with 5,142.

The London-based BGCI, which represents an estimated 2,500 botanic gardens around the world, used data from more than 500 published sources to create the list.

Of the 60,065 tree species, only around 20,000 have been assessed for their conservation status—of which 9,600 are threatened with extinction.

"BGCI's main reason for publishing the list is to provide a tool for people trying to conserve rare and threatened tree species," the organisation said in a statement.

"Currently, around 10,000 tree species are known to be threatened with extinction, largely by deforestation and over-exploitation.

"This number includes over 300 species that are critically endangered with fewer than 50 individuals remaining in the wild."

Aside from the Arctic and the Antarctic where there are no trees, the Nearctic region—comprising most of North America—has the lowest diversity, with less than 1,400 tree species.

The database will be continually updated, as around 2,000 new plants are discovered and described each year.

Source: AFP [April 05, 2017]

byUnknown

in Brazil, Ecosystems, Endangered Species, Environment, Natural Heritage, Rainforests

April 05, 2017

First world survey finds 9,600 tree species risk extinction

The first ever global database of trees on Wednesday revealed that 9,600 tree species are threatened with extinction and identified a total ...

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Future CO2 and climate warming potentially unprecedented in 420 million years

New research led by the University of Southampton suggests that, over the next 100 to 200 years, carbon dioxide concentrations in the Earth's atmosphere will head towards values not seen since the Triassic period, 200 million years ago. Furthermore, by the 23rd century, the climate could reach a warmth not seen in 420 million years.

A living Ginkgo leaf (left) and fossil (right). Density of stomata in such leaves is proxy of atmospheric CO2 in past 
[Credit: Dana Royer]

The study, published in Nature Communications, compiled over 1200 estimates of ancient atmospheric carbon dioxide (CO2) concentrations to produce a continuous record dating back nearly half a billion years. It concludes that if humanity burns all available fossil fuels in the future, the levels of CO2 contained in the atmosphere may have no geologically-preserved equivalent during this 420 million year period.

The researchers examined published data on fossilised plants, the isotopic composition of carbon in soils and the oceans, and the boron isotopic composition of fossil shells. Gavin Foster, lead author and Professor of Isotope Geochemistry at the University of Southampton, explains: "We cannot directly measure CO2 concentrations from millions of years ago. Instead we rely on indirect 'proxies' in the rock record. In this study, we compiled all the available published data from several different types of proxy to produce a continuous record of ancient CO2 levels."

This wealth of data shows that CO2 concentrations have naturally fluctuated on multi-million year timescales over this period, from around 200-400 parts per million (ppm) during cold 'icehouse' periods to up to 3000 ppm during intervening warm 'greenhouse' periods. Although evidence tells us our climate has fluctuated greatly in the past (with the Earth currently in a colder period), it also shows the current speed of climate change is highly unusual.

Carbon dioxide is a potent greenhouse gas and in the last 150 years humanity's fossil fuel use has increased its atmospheric concentration from 280 ppm in the pre-industrialisation era to nearly 405 ppm in 2016. However, it's not just CO2 that determines the climate of our planet, ultimately it is both the strength of the greenhouse effect and the amount of incoming sunlight that is important. Changes in either parameter are able to force climate change.

"Due to nuclear reactions in stars, like our sun, over time they become brighter," adds co-author Dan Lunt, Professor of Climate Science at the University of Bristol. "This means that, although carbon dioxide concentrations were high hundreds of millions of years ago, the net warming effect of CO2 and sunlight was less. Our new CO2 compilation appears on average to have gradually declined over time by about 3-4 ppm per million years. This may not sound like much, but it is actually just about enough to cancel out the warming effect caused by the sun brightening through time, so in the long-term it appears the net effect of both was pretty much constant on average."

This interplay between carbon dioxide and the sun's brightness has fascinating implications for the history of life on Earth. Co-author Professor Dana Royer, from Wesleyan University in the US, explains: "Up until now it's been a bit of a puzzle as to why, despite the sun's output having increased slowly over time, scant evidence exists for any similar long-term warming of the climate. Our finding of little change in the net climate forcing offers an explanation for why Earth's climate has remained relatively stable, and within the bounds suitable for life for all this time."

This long-term view also offers a valuable perspective on future climate change. It is well recognised that the climate today is changing at rates well above the geological norm. If humanity fails to tackle rising CO2 and burns all the readily available fossil fuel, by AD 2250 CO2 will be at around 2000 ppm - levels not seen since 200 million years ago.

Professor Foster adds: "However, because the Sun was dimmer back then, the net climate forcing 200 million years ago was lower than we would experience in such a high CO2 future. So not only will the resultant climate change be faster than anything the Earth has seen for millions of years, the climate that will exist is likely to have no natural counterpart, as far as we can tell, in at least the last 420 million years."

Source: University of Southampton [April 04, 2017]

byUnknown

in Ancient Environment, Climate Change, Environment, Fossils, Geology, Natural Heritage

April 04, 2017

Future CO2 and climate warming potentially unprecedented in 420 million years

New research led by the University of Southampton suggests that, over the next 100 to 200 years, carbon dioxide concentrations in the Earth...

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Scientists publish study on glacial carbon cycle

Two Montana State University researchers have played a major role in discovering how microbial communities in melting glaciers contribute to the Earth's carbon cycle, a finding that has global implications as the bulk of Earth's glaciers shrink in response to a warming climate.

The Cotton Glacier stream in the McMurdo Dry Valleys region of Antarctica, where MSU researchers 
Heidi Smith and Christine Foreman sampled glacier runoff in 2012, in shown in this aerial photo 
[Credit: Christine Foreman]

Heidi Smith, a postdoctoral researcher, and Christine Foreman, associate professor of chemical and biological engineering, both of the Center for Biofilm Engineering in MSU's College of Engineering, were co-authors of a paper published in the prestigious journal Nature Geoscience.

Titled "Microbial formation of labile organic carbon in Antarctic glacial environments," the article was co-authored by researchers at the University of Colorado at Boulder, the U.S. Geological Survey, Stockholm University in Sweden and the Max Planck Institute for Marine Microbiology in Germany.

The paper challenges the prevailing theory that microorganisms found in glacial meltwater primarily consume ancient organic carbon that was once deposited on glacial surfaces and incorporated into ice as glaciers formed.

"We felt that there was another side to the story," said Smith, the paper's lead author. Smith earned a Ph.D. in ecology and environmental sciences in MSU's Department of Land Resources and Environmental Sciences in 2016, with Foreman as her adviser.

"What we showed for the first time is that a large proportion of the organic carbon is instead coming from photosynthetic bacteria" that are also found in the ice and that become active as the ice melts, Smith said. Like plants, those bacteria absorb carbon dioxide and in turn provide a source of organic matter.

The research team made the discovery after sampling meltwater from a large stream flowing over the surface of a glacier in the McMurdo Dry Valleys region of Antarctica in 2012.

Afterward, Smith spent two months at the Max Planck Institute for Marine Microbiology in Bremen, Germany, with support from the National Science Foundation's flagship interdisciplinary training program, the Integrative Graduate Education and Research Traineeship. There, she worked with colleagues to track how different carbon isotopes moved through the meltwater's ecosystem, allowing the team to determine the carbon's origin and activity.

The researchers ultimately found that the glacial microbes utilized the carbon produced by the photosynthetic bacteria at a greater rate than the older, more complex carbon molecules deposited in the ice, because the bacterial carbon is more "labile," or easily broken down. The labile carbon "is kind of like a Snickers bar," meaning that it's a quick, energizing food source that's most available to the microbes, Smith said.

Moreover, the researchers found that the photosynthetic bacteria produced roughly four times more carbon than was taken up by the microbes, resulting in an excess of organic carbon being flushed downstream. "The ecological impact of this biologically produced organic carbon on downstream ecosystems will be amplified due to its highly labile nature," Foreman said.

Although individual glacial streams export relatively small amounts of organic carbon, the large mass of glaciers, which cover more than 10 percent of the Earth's surface, means that total glacial runoff is an important source of the material. Marine organic carbon underpins wide-ranging ecological processes such as the production of phytoplankton, the foundation of the oceans' food web.

As glaciers increasingly melt and release the organically produced, labile carbon, "we think that marine microbial communities will be most impacted," Smith said. "We hope this generates more discussion."

In a "News and Views" commentary accompanying the article in Nature Geoscience, Elizabeth Kujawinski, a tenured scientist at Woods Hole Oceanographic Institution, called the team's work "an elegant combination" of research methods.

Taken together with another study published in the same issue of Nature Geoscience, about microbial carbon cycling in Greenland, Smith's paper "deflates the notion that glacier surfaces are poor hosts for microbial metabolism," according to Kujawinski. The two studies "have established that microbial carbon cycling on glacier surfaces cannot be ignored," she added.

Source: Montana State University [April 04, 2017]

byUnknown

in Antarctic, Biology, Climate Change, Ecosystems, Environment, Natural Heritage

April 04, 2017

Scientists publish study on glacial carbon cycle

Two Montana State University researchers have played a major role in discovering how microbial communities in melting glaciers contribute to...

Read More