Sustainable Healthy Agricultural Ecosystems Ecology, Ecosystems, Production Ecophysiology, Food
Security: The Environmental Food Security Challenge of Realizing Stewardship the Virtuous Cycle
How do you sustainably or ecologically intensify agricultural production? 3 Pathways to Increase Production (Baudron et al., 2012) … a.k.a. Concept death by di- / trichotomy…
Ecological = Sustainable Intensification Four Premises Underlying SI (Garnett et al., 2013)
• The need to increase food production • Increased production must be met through higher yields because increasing the area of land in agriculture carries major environmental costs • Food security requires as much attention to increasing environmental sustainability as to raising productivity • SI denotes a goal but does not specify how it should be obtained or which agricultural techniques to deploy (recognition of the CA/panacea story)
Take home: Who can argue with this but how do you do it … What is Ecology? What is Ecology?
Ecology is not about: Stasis, Balance, Unconditional Synergies, Success for All… Ecology is about: Individuals → Populations, Communities, Ecosystems What is an “ecosystem”…? Key Definitions / Concepts (MA, Chap. 1) • Ecosystem: • “A dynamic complex of plant, animal, and microorganism communities & the nonliving environment interacting as a functional unit” (a temporary pond in a tree hollow to an ocean) • Ecosystem Services: • “the benefits people obtain from ecosystems” – include provisioning, regulating, supporting, cultural • Dual challenge to ES presented by goal of food security • Increased demand for ES • Simultaneous degradation in capacity of ecosystems to provide ES The ES Framework & linkages to human well-being (MA Chap. 1, Fig. 1.1) What is a healthy “ecosystem”…?
Harmonious? Balanced? In tune with the natural resource base?
W/ vs. W/o Humans? Does extinction occur in a “healthy” ecosystem? G X E = P: Genetics (development) interacts with Environment → Phenotype
Ecophysiology Ecophysiology is the study of how the environment, both physical and biological, interacts with the physiology of an organism. It includes the effects of climate and nutrients on physiological processes in both plants and animals, and has a particular focus on how physiological processes scale with organism size. Environment = Biotic & abiotic factors & their interactions Key ecological/eco-physiological concepts: Adaptations & Niches
Niches: Matching survival strategies to environments… (In Fitter & Hay, 2nd Ed. 1987) Acclimation versus Adaptation
• Acclimation: Plant physiological (& morphological) responses to environment to enhance survival/reproduction that require no genetic modification… Acclimation versus Adaptation
• Adaptation: Physiological (& morphological) changes in a population that have become genetically fixed by natural selection… Adaptation ~ the view from ecology… • What? Changes to better suit the organism (organ → ecosystem) to a condition or suite of conditions. • Easy to see when they can be seen in the context of the environmental driver: • Bird beak – seed size • Fur thickness – ambient temperature • Horses leg structure – swift predators • Less obvious but conceptually critical: Adaptations usually necessitate other adaptions & it’s the entire package that determines success • Swift predators ← horses leg structure ← horses tail structure (flies) … • Obvious (perhaps) and very critical: adaptations reflect the past • Only humans can “adapt” to changes that have not happened (and making those changes – if not necessary/useful yet – could be term “maladaptive”) Adaptation & C3 vs. C4 photosynthesis Map of Geographical Abundances of C3 and C4 Grasses in Savanna and Grassland Ecosystems
(Ehleringer, Cerling, and Dearing 2005.) C4 Photosynthesis is Adapted to Dry, Hot, Sunny Regions (right) and Struggles at Low Temps (left)
10°C C3 plants have an 35°C advantage at cool
temperatures <15 C C4 plant
C3 plant C3 plant Because
photorespiration Photosynthesis
Photosynthesis increases with temp. C C4 plant 4 plants have an advantage high temperatures >25 C Full sunlight Full sunlight Irradiance Irradiance
Because carbon-fixation in C4 plants is not carbon-limited, they are able to take advantage
of high light intensities; note that here C4 photosynthesis is not saturated in full sunlight Photorespiration Dramatically Limits C3 Photosynthesis at Higher Temperatures 60 330 ppm CO2 50 Photorespiration increases at high C4 temperatures because (a) Rubisco 40 selectivity decreases, and (b) and the
30 relative solubility of CO2 to O2 decreases. 20 By suppressing photorespiration, C4 photosynthesis can increase with sec)
- 10 2 C3 increasing T (to a certain level). 0
mol/m 60 1000 ppm CO μ 2 50
40 When photorespiration is suppressed by C4 increasing [CO2], or reducing [O2], C3 30 photosynthesis responds to increasing T like 20 C4 photosynthesis C3 10 Net photosynthesis Net photosynthesis ( 0 15 20 25 30 35 40 45 50 Leaf temperature (ºC)
Redrawn from Pearcy, R.W. and Ehleringer, J. (1984). Comparative ecophysiology of C3 and C4 plants. Plant Cell Environ. 7: 1-13. Critical Concept: Adaptations rarely “perfect” but perfection may not be worth it… • Example: Sickle cell anemia • Single amino acid mutation in beta chain of hemoglobin gene → sickle cell gene • Inherit from both parents → short life • Inherit from one abnormal & one normal? General prevalence outcome? • Inherit from one abnormal & one normal → protective advantage vs malaria • Outcome: high frequency of sickle cell trait where malaria is prevalent
Take home: Planning & implementing system level adaptations for SI ( and climate smart ?) agriculture is not trivial/easy… Example: Solving terminal heat stress in wheat… 3 adaptation strategies • Strategy 1: What is it? • Tolerance: Breed for improved heat tolerance at the critical point in crop development • Strategy 2: • Avoidance: Grow the crop such that the critical growth stage and stress event are no longer coincident • Strategy 3: • Grow something else better suited to the niche biophysical parameters
Take home: More than one way to skin a cat…