Friday, August 2, 2019

Carbon Capture Forests vs. Fields


Ever wonder what the relative capture of CO2 is from an acre of mature forest vs regrowth vs an acre of pasture or corn? For forests it goes like this: 

After harvest, for a few decades, forests are net sources of Carbon (C) to the atmosphere.  That is because the C capture from the atmosphere is low (no trees, low net primary productivity, NPP) and the C loss from the ecosystem to the atmosphere stays the same or increases after harvest because soil microorganisms keep eating soil organic matter and respiring it as CO2.

Then, at some point a few decades after harvest, things switch because tree C capture from the atmosphere increases to the point where NPP is greater than C losses from soil microbial decomposition.  After this switch, for hundreds of years, forests can be net sinks for atmospheric C.

In theory, at some point, an old growth forest should have net C capture of zero as inputs from NPP balance outputs from microbial respiration. In reality, there haven’t been many observations of this theoretical steady state – most forests have net C capture for centuries, but it becomes low in the oldest forests.

Rain fed agriculture, row crop or pasture, almost always has lower annual NPP than the adjacent mature forest vegetation.  However, whether an agricultural system has negative or positive net atmospheric C capture (the balance of NPP inputs and microbial respiration losses) depends a lot on how management practices have changed soil practices recently. 

Under some circumstances, reducing tillage can briefly turn ag systems into a C sink that accrues atmospheric C for a decade or so.  Conversion from annual to perennial vegetation, row crops to pasture, is even better – creating a large sink for atmospheric C for several decades by increasing storage of soil C. 

Like forests, row crops and pastures that have been under the same management regime for long times capture zero atmospheric C because NPP inputs to soil are balanced by microbial outputs. (This assumes all of the harvested product returns to the atmosphere as CO2 quickly when humans eat them or burn them for fuel). The time scales are shorter for these ag systems.  While forests might take centuries to reach this steady state, ag systems might take less than a century. (Jason Kaye, Professor of Soil Biogeochemistry, Penn State University)



For a comparison of carbon storage and accumulation in US Forests based on region and forest type check out the following paper by the US Forest Service: CarbonStorage and Accumulation in United States Forest Ecosystems

Fun Facts:
A 40 acre woodlot of relatively mature (50-year old) deciduous trees absorbs, or sequesters, approximately 30,000 pounds of carbon dioxide per acre in a typical year. And would be emitting about 22,000 pounds of oxygen per acre. The contribution varies with the age of the forest and species involved. (Timothy J. Fahey, Ecology Professor, Department of Natural Resources, Cornell University)

The EPA has calculated the amount of carbon dioxide emitted by the average car at about five metric tons, more than 11,000 pounds, so a single acre of woods would be countering the emissions of about 2.7 cars. For 40 acres, that would be about 109 cars.

Monday, July 29, 2019

Clemson Forestry Professor Writes Op-Ed on Threat of Forest Parcelization


I came across this piece in the Southern Regional Extension Forestry News. Great article highlighting the problems associated with parcelization which I highlighted in my previous post on urban sprawl on farmland. This post points out the same problems are occurring on forestland. 

Clemson University Forestry Professor, Dr. Thomas Straka, wrote an opinion article published by The Hill. Straka argues that wildfires and public lands aren’t America’s only forestry problem. Rather, the rapid parcelization that is occurring across the nation is a threat to family forests. Parcelization results from forest holdings being broken down into smaller parcels. Ultimately, smaller land holdings and more landowners will result in contradictory management goals/styles. Straka contends that these management problems will negatively affect the nation’s timber supply and provides recommendations on how to reduce parcelization impacts. I provided the article below.


Wildfires and public lands aren't America's only forestry problem
By Thomas J. Straka, opinion contributor — 07/22/19

Wildfires and contentious public land policy in the American West, sparking debate about climate change and forest management practices on public timberlands, seem to be the only forestry issues in the news. This suggests that problems with America’s forests are centered on federal land ownerships. Actually, forests owned by average folks are more likely to be a future problem. Lots of regular people own forests. These are called family forests and their future is important for the clean water, wildlife habitat, recreational opportunities and timber they produce.                   

The majority of the nation’s forests (443 million of 766 million acres) are in private ownership. Nearly two-thirds of that private forest is owned by families and individuals, mostly in small holdings. These became the family forests and the nation’s largest forest ownership group (owning 38 percent of forest, while the feds own only 31 percent).

Over the last 20 years, the number of family forest owners increased by over 1 million (to nearly 11 million). Considering just owners with more than 10 acres (eliminating the large backyards), average tract size of a family forest is 66 acres. That’s small by forestry standards.

At the time of the nation’s settlement, just over 1 billion acres was forested; today it is about three-quarters of that. This forest area has remained relatively stable over the past century.  Shifts in land use have helped maintain that stability; population growth and urban development ensure that won’t continue indefinitely.

To read the rest of the article click here.

Wednesday, July 17, 2019

What is the Impact of Suburban Sprawl?


I had a chance to see this first-hand a few weeks ago on my way out to Wyoming and back.  It was dramatic, the permanent loss of productive farmland was alarming to me.  The American Angus Association produced a documentary film on urban sprawl to demonstrate the impact of urbanization on rural America.  The film is called “Losing Ground.”  Check it out.  I provide the link to it on You Tube below.  



Morning Ag Clips
ST. JOSEPH, Mo. — Farmers and ranchers face a lot of challenges. Weather. Policy. Markets. One of the growing issues is the increasing urbanization taking over farm and ranch land across the U.S. To help spread awareness about this growing issue, the American Angus Association® produced the first film to expose the impact of urban sprawl on American Agriculture – “Losing Ground”—an I Am Angus® production.


The documentary features five Angus farm and ranch families who talk about the challenges and opportunities they have experienced with urban sprawl in their areas. The Lovin family, Lexington, Georgia; Marsh family, Huntley, Illinois; Stabler family, Brookeville, Maryland; Cropp family, Damascus, Maryland; and the Nelson family, Wilton, California, discuss how urban sprawl has impacted them, and American Farmland Trust CEO John Piotti talks about their research report “Farms Under Threat,” which shows the issue on a national level.

“It’s easy to drive through, especially the Midwest, and feel like we have plenty of land,” said Josh Comninellis, film director. “But, it’s a little more complicated than that as we dug into the research. Not only are we losing some of our best ground and a lot of total agricultural land, but the population, and therefore demand, is going up. When you pair those two things together, you see, down the road, a really dire situation emerging.”

According to the American Farmland Trust “Farms Under Threat” report, we’re losing 1.5 million acres a year, which breaks down to 175 acres every hour and three acres a minute. That trend is unsustainable, and a common ground needs to be reached between the population’s need for more housing and retail and agriculture’s need to produce food.

“There are a few documentaries out there talking about urban sprawl from an urban point of view, but there was nothing out there talking about the impact on farmland,” Comninellis said. “There is nothing talking about cities spreading and taking over farmland and the implication for our food supply. So, we decided to tackle the issue through the eyes of Angus producers, and we think ‘Losing Ground’ gives us the opportunity to help educate consumers while establishing connections with their rural counterparts.”

Education is the key to bridging the gap between farmers and ranchers and those who live in urban areas. The film strives to spread awareness for a rising issue for rural America and provide content for the agriculture community to share, as well.

For more information on “Losing Ground,” visit: http://www.angus.org/media/iamangus/losingground.aspx . Share the film with friends and neighbors.

June 12, 2019