Food, Agriculture, and Global Change

 

Outline:

•         Food and ecological processes

•         Food and evolution

•         Food and global change

•         Three global crises in food and agriculture
(and feasible remedies)

 

Food and global change

•         Agriculture has the greatest environmental impact of any human activity.

•         Agriculture and food are an engine of political and social change.

•         Food is a major determinant of human health.

•         Enough food is produced to feed the human population well, yet 1 billion people are chronically hungry.

 

Ecological processes

•         Food has been a focus for predation and competition throughout human evolution.

•         Agriculture occupies 40% of Earth’s land area today and is the primary cause of habitat transformation.

•         Human appropriation of net primary production (NPP0)

•         HANPP is the combined effect of “harvest” and productivity changes due to human influences.

•         Humans appropriated 24% of global NPP in 2000.

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Haberl et al. 2007, PNAS
 
 

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·         Cropland contributes 50% and grazing land 28.5% of the total HANPP.

Data from Haberl et al. 2007, PNAS
 
 

 

 

 

 

 

 


Evolutionary processes

Both natural and artificial selection have shaped our main food plants (and animals).

Artificial selection on teosinte to become corn

Changes in diets during human evolution have also changed us relative to our hominid ancestors:

  1. Reduction in size of molars and jaws
  2.  Shortening of digestive tract--reduction of gut volume
  3.  Digestive enzymes: higher levels of amylase (which converts starch to sugars) in humans than in chimps.

 

 

Crisis 1: Soil erosion

35% of agricultural land today is degraded by erosion.

Erosion rates (logarithmic scale) for different terrestrial regions compared with modern agricultural soils.

Cumulative plot of erosion rates compared to soil production rates: modern agriculture features erosion rates much higher than the rate of soil formation.

 

Crisis 1: Remedies

Soil erosion rate is lowest when land is covered in vegetation.

Thus, farmers should keep vegetation on the land year round.

 

Crisis 2: Agriculture and the loss of biodiversity

Agriculture is the major threat to biodiversity through habitat transformation, over-harvesting of wild species, introduced species, and pollution.

Percent of vulnerable U.S. species affected by different forms of habitat transformation

Agriculture (row crops)

33%

Land conversion for commercial development

35%

Water development

30%

Outdoor recreation

27%

Livestock grazing

22%

Pollutants

20%

 

 

Annual costs of pesticide use in the U.S.

Pesticides in drinking water

$1,126 million

Pollution, fish kills, monitoring

$161 million

Losses of wildlife

$207 million

Losses of bee colonies

$145 million

Acute effects in humans

$167 million

data from Leach and Mumford, 2008

 

Crisis 2: Remedies

Controversy over “land-sparing” versus “land-sharing”:
Practice industrial agriculture and set aside protected areas, or practice agriculture “in nature’s image” where conservation is the consequence of agriculture.

 

The Land Institute

•         Mission is to develop natural systems agriculture that runs on sunlight and generates its own fertility.

•         Native prairie as a model, with C3 grasses, C4 grasses, legumes, and sunflowers.

•         Perennials grown in mixtures.

•         Breeding perennial versions of annual grains and increasing yields and root systems of perennials.

 

Crisis 3: Unsustainable diets

Source:  Worldwatch Institute 2011: Nourishing the Planet

 

We already grow enough food to feed 9 billion people.

Cattle, pigs, and poultry consume 50% of wheat, 90% of corn, 93% of soybeans in the world--the food-equivalent of 2 billion more people.

Average U.S. consumption is 276 pounds of meat/person/yr.

 

Crisis impact of US foods

 

Shifting less than one day per week’s work of calories from red meat and dairy products to chicken, fish, eggs, or a vegetable-based diet achieves more GHG reduction than buying all locally sourced food.

 

 

Crisis 3: Remedies

Pasture-based rearing of livestock animals

Price animal products to reflect their actual costs

Reduce consumption of animal products

 

Summary

•         Harvesting food from wild species or raising domesticated species through agriculture have changed ecological interactions of humans with other species over the last 2 million years.

•         Evolutionary changes include selective breeding of domesticated species by human societies and changes in form (teeth and jaws) and physiology (enzymes) of humans in response to changes in diet.

•         Food and agriculture are the cause of major global environmental changes today.

•         Three global environmental crises caused by food and agriculture today all have potential remedies in the form of sustainable practices: keeping land covered in vegetation, growing a diversity of perennials plants together, and adjusting our diets to have a lower ecological footprint.