In a new study published by the journal Nature Sustainability, researchers call for a revised conservation paradigm that recognizes human and natural systems as inextricably intertwined and co-evolving and acknowledges the potentially positive roles that people play in generating ecosystem health through land stewardship. The researchers—representing Carnegie Museum of Natural History, Stanford University, and the Santa Cruz Mountains Stewardship Network—argue that revised conservation and sustainability science paradigms are integral to adapting to climate change and other anthropogenic stresses. Current frameworks—while recognizing the damaging impacts of society on nature and the positive contributions of nature to people’s wellbeing—gloss over people’s positive contributions to nature. This ignores the variability, complexity, and mutually constitutive states of culture, society, and ecologies. The researchers collaborated with the Santa Cruz Mountains Stewardship Network (SCMSN), located in a biodiversity “hot spot” and urban population center, as a case study assessment that incorporates land stewardship alongside other ecosystem health metrics and illuminates the challenges and opportunities for similar frameworks.
Historically, people lose access to land when it is set aside for conservation, ceasing land stewardship altogether due to the assumption that human activities can only diminish the biodiversity and health of wildlands. Recently, a return to diverse forms of stewardship—including using fire, harvesting timber, raising animals, and cultivating local food—has earned attention because of the benefits to managing ecosystem health in the face anthropogenic stresses, like invasive species and climate change. For example, in California, low-intensity grazing is useful for reducing invasive plants, while Indigenous cultural burning and restoration forestry are important tools for reducing the impacts of large, severe fires that are increasing with climate change. The researchers concede that challenges lie in identifying appropriate metrics to express stewardship geospatially and study its effects. Land stewardship is relationship-based, place-based, and dynamic. It is not easily classified, mapped, or quantified, and often occurs on private lands or in private contexts that are hard to study. Understanding and embracing the social-ecological complexities of land stewardship will prove critical for the future of conservation science.
“The threat and urgency of climate change and biodiversity loss is real, and as a society, we are not going to solve these problems without transformational shifts in our thinking and doing in all fields of practice.” said Dr. Nicole Heller, lead author and Associate Curator of Anthropocene Studies at Carnegie Museum of Natural History. “For too long, conservation science has promoted a worldview that eschews people from nature, ignoring valuable knowledge and mutually beneficial relationships people have with land and other species. This injustice has especially been the case with Indigenous populations and others with long cultural histories of stewardship in a specific place. The emerging paradigm shift, recognizing the value of land stewardship to ecosystem health, raises many interdisciplinary research questions and indicates an opportunity for more investment in caring for land stewards and land stewardship as part of protecting Nature. Re-thinking people and their possibility to be in good relationships with the land could be a game changer for sustainability.”
The study reflects one of Carnegie Museum of Natural History’s strategic commitments: to align research and programming around the “We Are Nature” concept, recognizing that humans are an inextricable part of nature—a powerful yet fragile relationship that has evolved over thousands of years. The museum debuted the We Are Nature podcast in 2022—the first season of which focused on local and regional climate action, including land stewardship—as a follow-up and companion to We Are Nature visitor experiences in the museum in 2017 and 2021.
In addition to Dr. Heller, the paper’s authors include Dr. Kelly McManus Chauvin, Jasper Ridge Biological Preserve and Department of Biology, Stanford University; Dylan Skybrook, Santa Cruz Mountains Stewardship Network; and Dr. Anthony Barnosky, Jasper Ridge Biological Preserve, Stanford University and Department of Integrative Biology, University of California, Berkley. Additional information about the study and SCMSN, including a conversation with the researchers, is available at Stanford News.
Anthropocene Section
Feeding the Monster in the Sewer
Water is a resource that I often take for granted. I take daily showers, wash my dishes, and do my laundry without a second thought to the amount or quality of water that is used. I only experience small aspects of the natural water cycle on a daily basis, from a bit of condensation on a cold glass of water to the sporadic downfall of rain that occurs in Pittsburgh. The water cycle that I’ve learned about in school can be boiled down to: precipitation, surface runoff, infiltration, evaporation, and condensation; but how do I, as a human being, fit into all of this? What is the human water cycle and how have parts of the water cycle changed within the Anthropocene?

As intrigued as I was, I didn’t know enough about my own impact on the water cycle, so I took a deeper dive into learning about what was actually happening to the water that I used. In order to explore the concept of the human water cycle I needed to start by looking at infrastructure. In the case of water infrastructure, outside of irrigation, the water purification systems and sewage systems are some of the most impactful additions human beings have included into the planet’s water cycle. These infrastructural systems span thousands and thousands of miles underground, connecting houses, neighborhoods, and cities. And yet, at least for me, there was a vast mental disconnect between the water that flows underneath us and the water that we consume. I wasn’t sure how to visualize something that was happening underground, hidden away from sight. That’s when I learned about fatbergs.
In 2017 an 820 foot long mass weighing 130 metric tons was discovered in the sewers of Whitechapel in London, England. The same type of mass, weighing 42 metric tons was found in Melbourne, Australia during the outbreak of the COVID-19 virus, most likely due to the flushing of “toilet paper substitutes” (i.e. paper towels, sanitary products, facial tissues). These masses are called fatbergs and can be found in most major cities, especially those with older sewage systems like Pittsburgh. A fatberg is a solidified mass of fat, formed overtime in sewers, that sticks to the build-up of un-flushable sewage. Fatbergs cost hundreds of thousands of dollars to remove, and also reduce river and stream water quality by making sewer overflows more likely. In the Pittsburgh Area, whenever the combined storm and sanitary sewer system is overloaded, excess flow is dumped directly into the rivers.

Fatbergs are a human phenomenon that directly impacts both us and the greater environment. The sewer overflows that they cause impact both the built and natural environment, introducing pollutants such as human waste from our toilets and fats from our kitchen sinks into the living domain. But as harmful as they are, they can be easily prevented.
How, you ask? The solution is simple… don’t flush down anything other than toilet paper and bodily waste. But why? What makes toilet paper any different from other paper-like materials? The answer lies in the unique quality of the material that toilet paper is made up of. Unlike paper towels that use long fiber pulps, which improves the strength and absorptivity of the material, and facial tissues that contain additives that hold the fibers together, toilet paper is made using approximately 70% hardwood pulps with short fibers and 30% softwood pulps with longer fibers. Due to the hardwood pulps, once the toilet paper makes contact with water, the short fibers, which also help keep the toilet paper soft to touch, are able to untangle and fall away into smaller fragments, eventually dissolving into tiny bundles of short fiber that can easily flow through the sewage system.

Objects like ‘flushable wipes’, unlike toilet paper, take hours to days to break down. This means that just because we are able to flush something down, doesn’t necessarily make it safe for sewer and septic systems. If you want to try an experiment to explore this concept, try putting ‘flushable’ wipes and toilet paper into two separate containers of water. See for yourself what happens.
Fatbergs are all the more relevant to us during the times of the pandemic, especially in the United States. As people stay home, more objects that aren’t healthy for the sewage system are being flushed. Think about the times you flushed anything other than toilet paper. Are you feeding a potential fatberg in your neighborhood?
Daniel Noh is an intern for the Center for Anthropocene Studies, Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.
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From the Allegheny to Our Kitchen Sinks
From the Allegheny to our Kitchen Sinks
There are more than 326 million trillion gallons of water on our planet. Our bodies are made up of around 60% water. Even the air that we breathe has water vapors in it. Water is everywhere, but the water we can use is limited. According to the National Groundwater Association, the Earth is made up of about 71% water. Out of that, 99.7% is trapped in oceans, icecaps, soil, and the atmosphere. That leaves us with around 0.3% of the Earth’s water to use and drink. The same water that all living and nonliving things have used again and again since water has been on the planet.

Every morning I go downstairs to the kitchen and pour myself a glass of cold water from a water filter. Without a second thought, I drink the water because I consider this water to be safe. After all, the porous, activated carbon filters absorb various chemicals, including chlorine, lead, and mercury, which ‘purifies’ the water. Furthermore, I don’t have to worry about what could be in the water, because I know that the water is thoroughly cleaned before it enters the house. But how is it cleaned? Where does this water come from and what does it go through in order to splash into my kitchen sink?
Let’s start with a broader concept: rivers. Most major cities can be found along rivers: Paris along the Seine River, London along the River Thames, Seoul along the Han River, and New York along the Hudson River. This is no surprise, as communities need fresh, drinking water as an essential part of building a city. Pittsburgh is no different. In fact, in Pittsburgh, two rivers, the Monongahela and the Allegheny form a third, the Ohio, which on its passage through Pennsylvania, West Virginia, Ohio, Kentucky, Indiana, and Illinois, is the primary water source for over five million people. Within the city, the Allegheny River provides us, the people of Pittsburgh, with fresh water that we use on a daily basis.

If my water comes from the Allegheny River, what’s the difference between drinking tap water and river water? That’s where the Pittsburgh Water and Sewer Authority, or the PWSA, enters the picture. PWSA is the organization in charge of providing quality water throughout the city of Pittsburgh. The organization’s drinking water system “contains approximately 965 miles of water lines, five reservoirs, and 11 tanks with a water storage capacity of 455 million gallons” (pgh2o.com). And their process for making clean water looks like this. First, the collected river water is coagulated using ferric chloride, potassium permanganate, carbon, and catatonic polymer, which react to the polluting particles in the water, causing them to stick and clump together. The water is then taken through the filtration process, where it flows through pulverized anthracite coal and sand to remove any of the remaining particles. Afterwards, the water is disinfected with sodium hypochlorite, a type of chlorine compound that is used to remove microbial particles. Lastly, once the water has been completely purified, fluoride, the processed form of a naturally occurring mineral, is added back into the water as recommended by the Center for Disease Control to prevent tooth decay.

As complex as this purification process is, it isn’t perfect. The quality of the water that we receive is affected by what we put into it and there are countless compounds that cannot be completely filtered out by the processes used in water treatment plants. For example, trace amounts of dioxane, a likely human carcinogen from plastic manufacturing runoff, can be found in Pittsburgh’s own water system. Moreover, as of 2019, the PWSA has introduced orthophosphate in order to reduce lead levels, originating from the city’s ancient water pipes, in our tap water. In the end, all the water treatment plants can do is clean the water, test for contaminants, and research new ways to produce and deliver as clean a product as possible. The rest is up to us, the community. It’s up to us to be cautious of how we treat water by watching what we flush, preventing littering, or even reducing plastic use to reduce both microplastics and plastic production.
Water treatment is a growing process; new methods to remove previously unfilterable chemicals are constantly being discovered. With this in mind, think about your relationship with water. How do you treat it? What kind of objects do you flush down the toilet? What are your direct and indirect interactions with our water system? All of our actions matter. Because what we put into the river, will eventually come back to us.
Daniel Noh is an intern for the Center for Anthropocene Studies, Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.
Resources
https://blogs.scientificamerican.com/guest-blog/the-purest-of-them-all/
https://www.portpitt.com/pages/monongahela-river
https://www.wpxi.com/news/what-you-need-to-know-about-pittsburghs-three-rivers/739536503/
http://www.orsanco.org/river-facts/
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The Zebra Mussel and the Shopping Cart
Zebra mussels (Dreissena polymorpha) are eastern European freshwater bivalves that invaded North America. Something unusual about their biology facilitated this invasion.
In marine waters, many benthic (living on the bottom) animals add their babies to the plankton, the mix of small and microscopic organisms largely adrift in the water column.
The situation is different in freshwater where almost all benthic animals lay their eggs on the bottom. (Freshwater plankton exist, but the organisms that compromise it spend their whole lives as plankton.) I don’t know why marine and freshwater animals differ that way, but they do. Zebra mussels are a major exception to this rule; they live in freshwater, but they put their babies (larvae) in the plankton.
How did zebra mussels invade North America? Partially loaded ships require ballast to safely navigate at sea. Decades ago, ships were loaded with rocks and dirt (and slug eggs) as ballast, and when they reached their intended port these materials were removed and replaced with cargo. That is why so many invasive slugs (essentially all your garden slugs are non-native) arrived first in seaports and spread from there. Ballast tanks that can be easily filled with water and drained are a design feature of modern ships, and depending upon some ship’s departure points, their ballast water sometimes contains larval zebra mussels. For many years, ships were slow enough that zebra mussel larvae arrived in North America dead, but eventually reductions in ocean crossing time worked in the invaders’ favor. In 1988 some larval zebra mussels arrived alive in the ballast water pumped out into Lake St. Clair near Detroit. By 1990, zebra mussels had infested all the Great Lakes and now they occur in more than half of the 50 United States.

The economic and ecological devastation caused by zebra mussels is legendary. Zebra mussels make threads (byssal threads) for attaching to hard objects. They clog intake pipes of city water supplies and power station cooling pipes, requiring costly removal. They compete with native mussels and young fish for food and can smother or hinder movements of our native mussels, snails (Fig. 1), and crayfish when they settle in large numbers.

A noteworthy item that became encrusted with zebra mussels is a shopping cart that was dredged out of Lake Superior in 2012. A replica of the shopping cart was on display during the We Are Nature exhibit at Carnegie Museum in 2018 (Fig. 2).
Lest you think I am biased against zebra mussels, I will note two possibly positive things you can say about them. First, they filter water efficiently and because they pump up to a liter (quart) per day, they cleaned up the formerly polluted water in Lake Erie. But even that can be negative, because they removed so much plankton from the water that our native species now have a hard time finding enough to eat. Second, because zebra mussels selectively concentrate certain toxic metals, including uranium, they have potential to be used in bioremediation efforts to clean water of this radioactive pollutant (Immel et al. 2016). But those are the only good things you can say about them. Mostly, they wreak havoc.
Literature Cited
Immel, F., Broussard, C., Catherinet, B., Plasseraud, L., Alcaraz, G., Bundeleva, I. & Marin, F. 2016. The shell of the invasive bivalve species Dreissena polymorpha: biochemical, elemental and textural investigations. PloS One, 11(5): e0154264. https://doi.org/10.1371/journal.pone.0154264
Timothy A. Pearce, PhD, is the head of the mollusks section at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.
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The inequity of summer heat

Ah, summertime! In Pittsburgh, after months of cold, grey days, the warm temperatures and sunshine bring a collective sigh of relief. Plants are roaring back, coloring the world green. Animals are out and about singing and foraging; people are picnicking, barbequing, gardening. Life feels abundant. But summer can quickly become oppressive, even deadly, if it gets too hot. Extreme heat is among the deadliest weather-related phenomena in the US, and cities are most at risk for this hazard.
The concentration of impervious surfaces and low-rise buildings in cities raises temperatures significantly, creating what is termed the urban heat island effect. Temperatures in a single urban area can vary as much as 18 F depending on the density of the grey stuff (buildings, sidewalks, roadways, and parking lots) relative to the green stuff (trees, parks). The urban heat island effect also interacts with global climate change. Rising temperatures due to emissions of heat-trapping gases from the extraction and burning of fossil fuels is making urban communities increasingly vulnerable to extreme heat. And like so many other pressing issues in the early summer of 2020, namely the coronavirus pandemic and police violence, extreme heat is experienced inequitably.
In the US, communities of color and resource limited communities are both disproportionately exposed and sensitive to extreme heat. One recent study explores this climate inequity and its relationship to the historic racially discriminating housing policy, called ‘redlining’. In an analysis published in the journal Climate in January 2020, Jeremy Hoffman, Chief Scientist at the Science Museum in Virginia, and colleagues ask: “do historical policies of redlining help to explain current patterns of exposure to intra-urban heat in US cities? and how do these patterns vary by geographic location of cities?” As the study describes, in the 1930s, redlining distinguished neighborhoods that were considered “best” (outlined in green) and “hazardous” (outlined in red) for investment by the Home Owner’s Loan Corporation, a federally funded program. Categorization on a scale from A (best) to D (hazardous) was based largely on racial makeup. The program prioritized white neighborhoods for economic investment and access to credit. While the practice ended in 1968 with passage of the Fair Housing Act, its legacy has persisted in structuring the social-economic and ecological landscape of US cities today. The study examines the pattern of land surface temperatures in cities today in relation to historic housing policy.
The results for 108 urban areas in the United States can be explored in an open access article, and also shared through an explorable map. Overall, Hoffman and colleagues found that yes, for 94% of US cities, historical policies of redlining track surface land temperatures. Historically redlined neighborhoods are about 5 degrees F warmer on average today than historically greenlined neighborhoods. While temperature patterns within a city are complex and influenced by microclimates and other factors, the authors argue that the heat burden in redlined neighborhoods has been aggravated by housing policy. Redlined neighborhoods have significantly fewer trees, and an abundance of public highway projects and large building projects that create especially high asphalt to vegetation ratios.
Examining the map of the analysis in Pittsburgh, shows a complex relationship between redlining and land surface temperature, part of which I would guess reflects our extremely variable topography and a complex history of shifting neighborhood demographics associated with the boom and bust of the steel industry. I encourage you to investigate the results yourself.
Hoffman’s research demonstrates how structural inequities and institutional racism in the US affects people’s differential experience with the Anthropocene. Anthropocene challenges, like global warming and global pandemics, reveal the coupled dynamics among human social-economic-political systems and ecological-climate systems. They reveal the way that discriminatory race-based policies from the past animate the present. The experience of the pandemic, the experience of summer heat, the experience of poor air quality, the experience of police violence, the list goes on, are not evenly felt across communities. In the US, research shows time and time again that low resource communities and communities of color are disproportionately suffering. In the processes of doing sustainability and adaptation to address the Anthropocene, the work of undoing injustice is essential. In the case of increasing urban heat, as cities adapt, an important research and practice will involve work to ensure greening policies undo racial discriminatory neighborhood investing practices, while also ensuring protection from gentrification and displacement.
Putting research into practice, Hoffman in his role at the Science Museum of Virginia, is collaborating with youth community organization, Groundwork RVA, to build solutions to urban heat that are both low-cost and high impact. At CMNH’s Center for Anthropocene Studies we are inspired and motivated by the role that museums are playing in empowering communities to understand global change and build social equity and resilience.
Nicole Heller is Curator of Anthropocene Studies at the Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences working at the museum.
Hip and “Trashy” Ice Cream

I grew up in the country, on a gravel back road where the diary truck drove by to fill its tank at the local dairy farms. Those cows, I know now, were living the high life. Grazing idyllic in oak tree savanna fields, with miles of territory to wander. I knew the farmers’ kids. I even helped them with their chores, although not often because it wasn’t fun, even though they said it would be.
My assistance did result in my first taste of milk squirted straight from the udder! The term “Organic” was not used then, but now I know those were family owned organic farms in every sense of the term. No hormones. No cages. Hey, the farm kids even gave the cows names! At the time, my mom would buy name brand ice cream from the town’s market. My favorite was mint chocolate chip ice cream (the green kind). The flavor is super hip right now for being a “trashy” flavor. When I say hip and trashy, I mean in a weird nostalgic unhealthy food like tater tots and grilled cheese kind of way. Some basic research reveals those cheap ice creams were, for their time, wholesome, waaaayyyy more wholesome than they are now.
Things have since changed in my hometown. Those family owned dairy farms are gone, replaced with mega dairy farms. And ice cream, especially my favorite trashy and hip flavor, has changed into what I consider to be really unhealthy in an environmentally unfriendly way. Palm oil. You might not know this, but palm oil is an ingredient in most frozen desserts and frozen dairy desserts (ice cream with a sub label). Palm oil is high in saturated fat and can affect cardiovascular health. The FDA does not require palm oil to be labeled, and instead the term vegetable oil is frequently substituted. Because most palm oil plantations are unsustainable, their spread across the landscape threatens rain forests, causes habitat loss for endangered species, violates human rights, and impacts climate change. Most name brand ice cream manufacturers currently use the stuff, but don’t want to be identified with its impacts. Carnegie Museum of Natural History’s Assistant Curator of Amphibians and Reptiles, and tropical conservation ecologist Jennifer Sheridan has some serious concerns about the palm oil industry and has witnessed firsthand its impacts on rainforest ecology. Check out her work here.
So how do I fix this? Or maybe, how do I get my chocolate mint chip ice cream fix?
First off, during the pandemic, I’ve been making homemade ice cream. I’ve been able to control the ingredients and add in special touches like fresh mint (growing out of control in my neighbor’s garden). Here’s a quick blender recipe I’ve used. When I need ice cream from the store for my movie binges, I choose companies that clearly label their ice cream to be palm oil free. Ben and Jerry’s does this very well. As the ice cream shops open up, I will go local.

All of these options may seem high priced or too much work. Surprisingly the homemade recipes are really easy to make, and pretty cheap considering the quality of ice cream produced. The great thing is you can enjoy the process, sit back and not feel guilty about using palm oil, the really unhealthy and not cool ingredient in ice cream. And for me, it takes me back, to when ice cream had ingredients I could point to.
Asia Ward is CMNH Anthropocene Program Manager and Science Communication Fellow. Museum staff, volunteers, and interns are encouraged to blog about their unique experiences and knowledge gained from working at the museum.