Cows and bison are often compared when discussing their contributions to greenhouse gas emissions, especially methane. But do bison really produce as much methane as cows? In this article, we’ll take a closer look at the available research and try to separate fact from fiction.
An Important Distinction: Cattle vs Bison
First, it’s important to note the distinction between cattle and bison. Cattle refers to domesticated bovine animals like cows, steers, and bulls. Bison are their wild, undomesticated cousins that once roamed North America in huge herds.
While they belong to the same family and look similar, they have different behaviors, diets, and digestive systems that likely impact their methane production So we can’t assume bison methane equals cattle methane More research is needed.
Methane Matters
But why does it matter how much methane cows vs bison produce?
Methane is a powerful greenhouse gas, trapping heat in the atmosphere. Cattle are a major source, contributing about 4% of total US greenhouse gas emissions through belching and manure.
So comparing historic bison numbers to modern cattle numbers, as some social media posts do, misses the point The goal should be understanding and reducing methane from all ruminants
Estimating Historic Bison Methane
Bison once numbered 30-60 million in North America. A 2012 study estimated they produced around 1.8 billion kg of methane yearly before European settlement.
For context, 42 million modern dairy and beef cattle likely produce over 4 billion kg yearly.
So historic bison methane was substantial but possibly lower than cattle today. However, many uncertainties remain around historic bison diet, size, and methane yield.
The Diet Difference
Diet likely explains part of the methane gap between bison and cattle.
One 1998 study found bison fed alfalfa pellets in captivity produced about 30 kg of methane yearly. But cattle eating typical commercial diets produce around 100 kg yearly.
Free-roaming bison ate wild prairie grasses and selectively grazed fresh foliage – a diet that may generate less gas than cattle feed. More research is needed comparing methane from grass-fed cattle vs grazing bison.
Safety Challenges
What makes comparing bison and cattle methane difficult? Bison are wild, dangerous animals.
Measuring methane requires close proximity to the animal’s mouth – hard to do safely with bison. Cattle are domesticated and easier to monitor.
One 2021 study used cameras and footprint modeling to estimate bison methane from a distance. But more work is needed with free-roaming herds.
The Bottom Line
While some claim bison farting didn’t impact historic climate, methane matters regardless of the source. Cattle, bison, and other ruminants all contribute.
But bison likely produced less methane than cattle today due to diet, size, and digestive differences. More research is needed to quantify bison methane, especially from wild herds.
Reducing methane should be the goal, not dismissing it. And understanding methane production from historic bison herds and modern cattle herds can help guide low-emission grazing practices.