15 December 2017

House Bugs

Welcome to Warren’s Notice. In case you didn’t take notes when reading last Friday’s blog post, I’ll remind you that, globally, spiders devour some 400 to 800 million metric tons of insects each year, and over 95% of that total is attributed to spiders in forest and grassland (Spiders’ Sumptuous Repast).

Even if you didn’t see the post, you’re likely aware that a few non-forest, non-grassland spiders may reside in your home. They’re there for a reason, which is to say they’re not going hungry. I can say that because a recent study offered insight into the arthropod populations in our homes. 

Simulated arthropod in the house.
Bug Terminology
Before continuing, I must note that arthropods are animals with no spine, a hard outer skin and legs with bones joined together. They include insects (beetles, bees, ants, flies, moths), arachnids (spiders), myriapods (centipedes, millipedes) and crustaceans (wood lice, crabs and shrimp).

“Bugs” is a colloquial term for any insect class and small arthropod. True bugs are hemipterous insects--those with forewings and mouthparts modified for piercing and sucking, such as cicadas and aphids.

Now, back to the research.

House-Sharing Arthropods
Collaborating scientists affiliated with the California Academy of Sciences, North Carolina State and Rutgers universities and the Natural History Museum of Denmark examined how arthropod diversity and composition are influenced by the layout of our houses as well as by our lifestyles.

Entomologists surveyed and exhaustively sampled living and dead arthropod specimens in every room of 50 houses within 65 kilometers (about 40 miles) of central Raleigh, North Carolina.

They collected over 10,000 specimens of 304 arthropod taxonomic families. The houses, which averaged 41 years in age (7 to 94), hosted an average of 62 distinct arthropod families (24 to 128).

To assess the occurrence and distribution of arthropods among rooms and the influencing factors, the researchers categorized 531 rooms as attics, basements, bathrooms, bedrooms, common rooms or kitchens; carpeted or bare-floored; and occupying the subterranean, ground or above-ground house level.

Of the 304 arthropod families encountered, they included only those families found in at least 20 of the 50 houses, in at least 4 rooms in a house.

What and Where Were the Arthropods?
Some key findings of the analysis were:

- Most arthropod species were not primarily indoor inhabitants but simply filtered from the outside.
- As the number of doors and windows increased in a room, so too did the arthropod diversity.
- Arthropod diversity in rooms tended to decrease the higher the floor level.
- Basements and common rooms appeared to host arthropod communities with significantly different compositions compared to the more homogenous communities of bathrooms, kitchens and bedrooms.
- Arthropod communities in all rooms exhibited a food-chain (trophic) structure with predators (spiders, ground beetles), house-associated scavengers and fungus feeders (ants, carpet beetles, book lice, drain flies, silverfish) and transients from outdoors (non-feeding flies, leafhoppers, springtails).
- Carpeted rooms had greater arthropod diversity than did rooms with bare floors.
- Arthropod diversity and composition did not vary significantly based on presence of cats or dogs, number of houseplants, pesticide usage or relative levels of clutter and dust accumulation.

Graphic summary of house arthropod study findings. (From www.nature.com/articles/s41598-017-15584-2)
Wrap Up
Overall, the study found the indoor arthropods were largely a reflection of the outdoor arthropods and thus strongly influenced by access to the outside. Human behavior appeared to have little influence.

Though the study was relatively small, focused on only one geographic region, the work is expanding internationally. The results could be quite different in your area. Nevertheless, that they found an average of 62 arthropod families in the study area houses might induce you to invite a spider or two inside for animal control.

Thanks for stopping by.

House arthropods study in Scientific Reports: www.nature.com/articles/s41598-017-15584-2
Article on study on ScienceDaily website: www.sciencedaily.com/releases/2017/11/171110084322.htm

08 December 2017

Spiders’ Sumptuous Repast

“Spiders could theoretically eat every human on Earth in one year.” “Think spiders are freaky? Wait 'til you hear how much they eat.” Those were the headlines in The Washington Post and USA Today.

Welcome to Warren's Notice. Last March, I was all set to blog about a research study on the impact of spiders preying on insects. Then I noticed even our local Wisconsin newspaper had a few sentences on the study findings. I decided to let the topic pass.

Banana spider catching a wasp.
(photo from video
by Angelique Herring; 3:37 min)
But I didn’t delete my notes. And lately, I’ve been wondering. Maybe you missed all the reports. Maybe you’d like more detail than most news reports offered. Or maybe, seeing “spiders” in the headline was enough for you. (NB: Spiders do not dine on humans, not even for a snack.)

So, I’m back with the study. It’s not that the research will cure your arachnophobia or make you a fan of spiders. It’s just that the findings are too interesting to miss. Plus, the study complements other blog posts I've written about spiders (Spider Role Model, Web Addresses Addendum, Predator-Mimicking Moth).

Spiders Are Global Predators
Spiders are among the most common and abundant predators in the terrestrial environment. They’re found nearly everywhere, tropics to the Arctic. Over 45,000 species have been recognized thus far, and they’re all carnivores, feeding on insects and even other spiders. How much do they eat? That’s what the study was about.

Collaborating scientists from Switzerland’s University of Basel, Sweden’s Lund University and Germany’s Brandenburg University of Technology Cottbus-Senftenberg developed estimates of the weight of prey that spiders kill annually in different biome types and worldwide.

How Many Spiders Are There?
First, the researchers obtained a measure of spiders in the world. The literature provided 65 values of spider biomass (i.e., weight per unit area), which they were able to assign to seven terrestrial biomes: (1) tropical forests, (2) temperate and boreal forests, (3) tropical grasslands and savannas, (4) temperate grasslands (including old fields, permanent pastures, mown meadows) and Mediterranean shrublands, (5) annual cropland, (6) deserts and (7) Arctic tundra.

Combining the average biomass weight per unit area for each biome and the biomes’ areas, the researchers determined the total weight of global spiders to be approximately 25 million metric tons. (One metric ton is 1000 kilograms or about 2200 pounds.)  

Jumping spider attacking a fly.
(photo from video
by Andrew Huggins; 7:22 min)
How Much Do They Eat?
Next, the researchers estimated the weight of prey spiders kill annually. They used two different methods to validate their results.

The first method’s estimate was based on how much food spiders need. They combined the food requirements per unit body weight, derived from the literature, with their estimates of spiders’ weight per unit area for each biome.

The second method’s estimate was based directly on published assessments of spiders’ annual prey kill in selected biome types (e.g., prey censuses in the field combined with web density estimates).

Allowing for the range of estimates within biomes and accounting for factors such as reduced feeding on rainy days, the researchers arrived at total estimates of 460 to 700 million metric tons/year with the first method and 400 to 800 million metric tons/year with the second method. (That sentence should probably end with an exclamation point.)

Wrap Up
Putting the estimates together, the researchers concluded that the spiders’ global annual prey kill is in the range of 400 to 800 million metric tons/year. Over 95% of that is attributed to spiders in forest and grassland biomes.

So, before you swat, step on or vacuum your next spider, you’ll have to decide. Do you want 400 to 800 million metric tons of assorted insects or 25 million metric tons of spiders. As one of the other headlines from last March read, “Spiders eat twice as much animal prey as humans do in a year.” Thanks for stopping by.

Global spider prey kill study in The Science of Nature journal: link.springer.com/article/10.1007%2Fs00114-017-1440-1
Example articles on the study:

01 December 2017

Wake Up, World!

Welcome to Warren’s Notice. I’m going to guess that, 25 years ago, you missed the “World Scientists' Warning to Humanity.” I did, or at least, I don’t remember it.

The 1992 World Scientists’
Warning to Humanity was
organized by the Union of
Concerned Scientists.
The 1992 Warning was an appeal from more than 1700 of the world’s leading scientists, including most Nobel science laureates, for humans to stop inflicting harsh and often irreversible damage on the environment and critical resources. If unchecked, they wrote, we may so alter the world that it will be unable to sustain life as we know it.

Led by the Union of Concerned Scientists, the short warning didn’t waste a lot of words in identifying areas that must be addressed across the spectrum of the environment--atmosphere, water resources, oceans, soil, forests, living species--and population. The scientists called, for example, for the world to cut greenhouse gas emissions and pollution of air and water, halt deforestation, reverse the trend of collapsing biodiversity and stabilize population.

Well, even if you and I weren’t paying attention 25 years ago, we’ve got another wake-up call: the "World Scientists' Warning to Humanity: A Second Notice." And this time, there are a lot more people calling. Led by scientists from Oregon State University and signed by nearly 15,400 scientists from 184 countries, the second warning picks up where the first warning left off.

Second Warning
Authors of the second warning used all available data to evaluate changes over time in the specific areas identified in the first warning: gases that deplete stratospheric ozone, freshwater resources, marine catch, ocean dead zones, forest acreage, vertebrate species abundance, carbon dioxide emissions, temperature change and both human and ruminant livestock population.

They found that, with the exception of one area--stabilizing stratospheric ozone, humanity has failed to make sufficient progress in addressing the challenges. All other areas have gotten worse over the past 25 years.

Among areas of special concern are the current trajectory of potentially catastrophic climate change due to rising greenhouse gases from burning fossil fuels, deforestation and the decline in species abundance. We have unleashed the sixth mass extinction event, wherein many current life forms could be annihilated or committed to extinction by the end of this century.

Example trends from World Scientists’ Warning to Humanity: A Second Notice. Darker portion of graphs show trend after the first warning in 1992. (Graphs from academic.oup.com/bioscience/advance-article/doi/10.1093/biosci/bix125/4605229)
Recommended Actions
Despite the success of lobbyists in delaying environmental progress, and in the face of the Trump administration’s actions, the authors of the second warning judge that with a groundswell of organized grassroots efforts, dogged opposition can be overcome and political leaders compelled to do the right thing. They also urge that we re-examine and change our individual behaviors.

Among the many examples they offer of diverse steps humanity can take to transition to sustainability are:

- devising and promoting new green technologies and massively adopting renewable energy sources while phasing out subsidies to energy production through fossil fuels

- prioritizing…well-funded and well-managed reserves for a significant proportion of the world's terrestrial, marine, freshwater and aerial habitats
- halting the conversion of forests, grasslands and other native habitats
- restoring native plant communities at large scales, particularly forest landscapes
- developing and adopting adequate policy instruments to remedy defaunation, the poaching crisis, and the exploitation and trade of threatened species
- promoting dietary shifts toward mostly plant-based foods
- further reducing fertility rates by ensuring that women and men have access to education and voluntary family-planning services.

Wrap Up
In response to the support the second warning has generated, the authors have established an Alliance of World Scientists (see P.S.).

The main goal of this new assembly of scientists is to be a collective international voice of many scientists regarding global climate and environmental trends and how to turn accumulated knowledge into action.

Scientists of any discipline are invited to visit the Alliance website to read and endorse the 1000-word second warning. Also available on the website are the list of the original signatories as well as a running list of subsequent endorsers, which was approaching 3800 at this writing.

Thanks for stopping by.

1992 World Scientists' Warning to Humanity: www.ucsusa.org/about/1992-world-scientists.html#.WgsMCTeQyUk
“World Scientists’ Warning to Humanity: A Second Notice” in BioScience journal: academic.oup.com/bioscience/advance-article/doi/10.1093/biosci/bix125/4605229
Example articles on second warning:

Alliance of World Scientists website: scientists.forestry.oregonstate.edu/

Example articles on science and the environment under Trump administration:
CBS News report on status of the White House’s Office of Science and Technology: www.cbsnews.com/news/donald-trumps-science-office-is-a-ghost-town/
TIME article on EPA under Pruitt: time.com/4998279/company-man-in-washington/
National Geographic list of how Trump is changing the environment: news.nationalgeographic.com/2017/03/how-trump-is-changing-science-environment/

24 November 2017

Climate Change Report

Surprise, surprise. The White House approved release of the Climate Science Special Report, the first of two volumes of the Fourth National Climate Assessment. Also, apparently none of the 13 Federal agencies responsible for producing the report tried to undercut or change the findings of its scientists.

Welcome to Warren’s Notice. So why was this all a surprise? In sharp contrast to the president’s words and his administration’s policies, the report’s executive summary states:  
This assessment concludes, based on extensive evidence, that it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century. For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence. [Bold type is from the report.]
Surface temperature change (in °F) for 1986–2015 relative to 1901–1960 from the NOAA National Centers for Environmental Information. (Graphic from Climate Science Special Report.)
Origin of Climate Report
It’s easy to forget that, once upon a time, Republican presidents were the environmental good guys. In 1970, for example, Richard Nixon created the Environmental Protection Agency, and he did it by executive order. The consensus is that his motivation was truly environmental.

Even closer to the topic, Ronald Reagan and George H.W. Bush actively promoted measures to combat climate change. One major action was the U.S. Global Change Research Program (USGCRP), established by presidential initiative in 1989 and mandated by Congress in the Global Change Research Act of 1990.

Member agencies of the
U.S. Global Change
Research Program.
The USGRP directed 13 Federal agencies to develop and coordinate a comprehensive and integrated United States research program which will assist the Nation and the world to understand, assess, predict, and respond to human-induced and natural processes of global change.

One mandated product of the USGRP is the National Climate Assessment. Every four years, the agencies prepare a report that analyzes both the effects of global change and the human-induced and natural trends in global change for the subsequent 25 to 100 years.

Fourth National Climate Assessment
The recently approved Climate Science Special Report is an authoritative, comprehensive 470-page, 15-chapter, 5-appendices assessment of the science of climate change with a focus on the United States. It was prepared by scientists in government and academia and peer-reviewed by the National Academy of Sciences.

Selected Key Findings
Each chapter of the report includes key findings with confidence statements. I've taken excerpts from several findings of high or very high confidence to convey the significance of the issues.

- [A]verage temperatures in recent decades over much of the world have been much higher, and have risen faster…than at any time in the past 1,700 years or more
- It is extremely likely that more than half of the global mean temperature increase since 1951 was caused by human influence on climate
- Stabilizing global mean temperature to less than 3.6°F (2°C) above preindustrial levels requires substantial reductions in net global CO2 emissions prior to 2040 relative to present-day values and likely requires net emissions to become zero or possibly negative later in the century
- The frequency and intensity of heavy precipitation events are projected to continue to increase over the 21st century
- Plant productivity has not increased commensurate with the increased number of frost-free days or with the longer growing season
- Arctic-wide ice loss is expected to continue through the 21st century, very likely resulting in nearly sea ice-free late summers by the 2040s
-Global mean sea level (GMSL) has risen by about 7 to 8 inches since 1900, with about 3 of those inches occurring since 1993
- Relative to the year 2000, GMSL is very likely to rise by 0.3–0.6 feet by 2030, 0.5–1.2 feet by 2050, and 1.0–4.3 feet by 2100 (very high confidence in lower bounds)
- Tidal flooding will continue increasing in depth, frequency, and extent this century.

Muir Glacier, Alaska, photographed by
U.S. Geological Survey in 1941 and 2004.
(From Climate Science Special Report.)
Wrap Up
The forthcoming second volume of the Fourth National Climate Assessment, Climate Change Impacts, Risks, and Adaptation in the United States, is expected by late 2018. 

The concern is that we’ve passed the global climate tipping point. Whereas the Paris climate agreement aimed to limit global warming to 3.6°F (2°C) above preindustrial levels, the UN climate negotiators are now forced to consider 5.4°F (3°C). The sea-level rise alone would impact hundreds of millions of people.

Although certain US states, cities and businesses are trying to step in to fill the role abdicated by our federal government, coordinated global action is critical. Let’s hope the report’s release signals a change. Thanks for stopping by.

Fourth National Climate Assessment, Volume I--Climate Science Special Report: science2017.globalchange.gov/
The U.S. Global Change Research Program for Fiscal Year 2017: downloads.globalchange.gov/ocp/ocp2017/Our-Changing-Planet_FY-2017_full.pdf
Richard Nixon and the EPA:

Reagan and Bush (41) on climate change policy: nsarchive2.gwu.edu/NSAEBB/NSAEBB536-Reagan-Bush-Recognized-Need-for-US-Leadership-on-Climate-Change-in-1980s/
Article on the 3°C world on The Guardian website: www.theguardian.com/cities/ng-interactive/2017/nov/03/three-degree-world-cities-drowned-global-warming?CMP=share_btn_tw
Interview with Al Gore re: Trump and climate on The Guardian website: www.theguardian.com/environment/2017/nov/10/al-gore-donald-trump-climate-change