The next step Lets take what we know about causal loop diagrams and begin to create a system dynamics model .. 1 2 3 Dynamic Feedback Loops in Flower Gardening Created by Paul Newton, Linda Tompkins, Marianne Krasny, and Karl North October 2004 Slightly modified by John Gerber for UMass Ag Systems Thinking Class January 2006 4 Behavior-Over-Time-Graph (BOTG) maximum possible Desired Future Flower production (flowers/year) Feared Future 0 2000 2004 2008 Year Student Problem Statement: What can we do to create the desired future? 5 So, lets develop a hypothesis for growth and decline in flower production using system dynamics .. Like this seeds + flower production s 1. The more flowers produced per year, the more seeds are produced 6 Here we have the basic causal loop + seeds + R flower production 2. And the more seeds, the more flowers are produced. R = + + ss 7 + seeds + R flower production soil quality 3. But more flower production, over time, also acts to decrease soil quality 8 Now we have a limits to growth archetype + o - seeds + R flower production B soil quality + s 4. Reductions in soil quality cause corresponding reductions in flower production. B = + 9 So, what can be done to reverse the trend in decline of soil quality? 1. xxx 2. yyy 3. zzz 4. What else? 10 desired flower production A possible remedy - + seeds + + R flower production B - B ? + soil quality + gardening practice quality (fertilizing, watering, weeding, etc.) 5. A response to declining soil quality might be an increase in good gardening practices! If they are effective, these practices will improve soil quality. 11 What kind of loop is this? desired flower production A possible remedy - + seeds + + R flower production B - B ? + soil quality + gardening practice quality (fertilizing, watering, weeding, etc.) 5. A response to declining soil quality might be an increase in good gardening practices! If they are effective, these practices will improve soil quality. 12 desired flower production + seeds + + R flower production B B soil quality + + gardening practice quality (fertilizing, watering, weeding, etc.) - Right, we have a new balancing loop (- + +), a decline in flower production increases good gardening practices and thus enhancing soil quality, and . 13 Outside influence desired flower production + seeds + + R flower production B B soil quality B + + + gardening practice quality (fertilizing, watering, weeding, etc.) - And flower production might slowly improve too! Next, lets assume the desire for more flowers increases. For now, this influence comes from outside the system (push the boundaries). 14 customers + desired flower production + seeds + + R flower production B B soil quality B + + + gardening practice quality (fertilizing, watering, weeding, etc.) - More Feedback Loops The more flower production, the more customers may be solicited to purchase them, and therefore the more customers. For now, customers isn t built into the system completely. 15 customers + R + seeds + + + R B B soil quality B + desired flower production + flower production + gardening practice quality (fertilizing, watering, weeding, etc.) - More Feedback Loops And more customers stimulates the production of more flower production. 16 customers + R + seeds + + + R B B soil quality B + R + desired flower production + flower production + gardening practice quality (fertilizing, watering, weeding, etc.) - More Feedback Loops And more customers increases the desire for flower production! (R ++++). Now both desire and customer are inside the system. That is, they are more integrated into our story or understanding. 17 + customers + R + seeds + + + + diseases R B B soil quality B + R + desired flower production + flower production + gardening practice quality (fertilizing, watering, weeding, etc.) - More Feedback Loops Of course, more flower production is likely to mean more flower diseases. 18 + customers + R + seeds + R B B + B + soil quality B + R + desired flower production + flower production - + gardening practice quality (fertilizing, watering, weeding, etc.) - + diseases More Feedback Loops And diseases will mean a decline in production (B -+). 19 + customers + R + seeds + R B B + B B +diseases R + soil quality B + R + desired flower production + flower production - + gardening practice quality (fertilizing, watering, weeding, etc.) - More Feedback Loops And more diseases is likely to mean an increase in gardening practices to prevent disease, maybe this time we include pesticides .. 20 + customers + R + diversity seeds + R B B + B B +diseases R + soil quality B + R + desired flower production + flower production - + gardening practice quality (fertilizing, watering, weeding, etc.) - More Feedback Loops But rather than relying on practices (like pesticides), what if we increase the diversity of types of flowers produced? Lets push the boundaries for a solution .. For now, diversity is outside the system. 21 + customers + R + diversity seeds + R B B + R ? B B +diseases R + soil quality B + R + desired flower production + flower production - + gardening practice quality (fertilizing, watering, weeding, etc.) - More Feedback Loops Diversity decreases disease, without pesticides. 22 + + customers R R B + diversity seeds + R + + R B B + R B B +diseases R + soil quality B + R + desired flower production + flower production - + gardening practice quality (fertilizing, watering, weeding, etc.) - More Feedback Loops And with more diversity customers are not only possible but needed! The picture is becoming more integrated. At this point we can stop with a relatively complete story. (Check it by reading the story again). 23 + seeds R + flower production Well, we ve come a long way haven t we? System Dynamics Modeling 24 Modeling Organic Matter Accumulation/Depletion in Agroecosystem Soils Okay, so lets figure this out! 25 The Situation according to Karlo Are these demonstrable facts, assumptions that may not be easy to test, or testable hypotheses? 1. Civilization as we know it, with its urban populations and advanced division of labor, requires agriculture. 2. Civilization requires a sustainable agriculture. 3. Sustainability of agriculture is dependent upon our willingness and ability to rebuild <a href="/keyword/soil-organic-matter/" >soil organic matter</a> . 26 The Problem according to Karlo In conventional agricultural systems, <a href="/keyword/soil-organic-matter/" >soil organic matter</a> tends to decline to 1% or less in the Northeastern U.S, which undermines productivity unless synthetic nutrients are used as a fertility crutch. Someone please explain this! 27 The Problem according to Karlo Conventional agriculture is a slowly moving disaster. Productivity per chemical input dollar increases slightly when inputs are first applied, and then declines even faster than it would otherwise due to reinforcing feedback loops that include spiraling fertilizer use, declining plant health and soil community health, and increasing chemical rescue therapy. Yikes . We need help here! Lets see if we can make sense out of this claim by using causal loops. 28 <a href="/keyword/soil-organic-matter/" >soil organic matter</a> Ecosystem Carrying Capacity 15%? Y-Axis 0 0 X-Axis 20 40 Years Under conventional tillage agriculture, <a href="/keyword/soil-organic-matter/" >soil organic matter</a> tends to decline to 1% or below in the Northeast unless it is replaced. Someone please explain this! 29 <a href="/keyword/soil-organic-matter/" >soil organic matter</a> Ecosystem Carrying Capacity 15%? Y-Axis Productivity/ Chemical $ Farm Productivity 0 0 X-Axis 20 40 Years Someone explain the green line! Then, the red one. 30 <a href="/keyword/soil-organic-matter/" >soil organic matter</a> Ecosystem Carrying Capacity 15%? Y-Axis Productivity/ Chemical $ Farm Productivity 0 0 20 X-Axis 40 Years According to Karlo productivity per dollar of chemical input increases at first and then declines rapidly due to several vicious cycles in the system. Lets look at them! 31 soil fertility + R Chem Welfare/Warfare soluble salt fertilizer use soil biological health - Someone please explain this! 32 soil fertility + R Chem Welfare/Warfare soluble salt fertilizer use soil biological health - According to Karlo . conventional fertilization, while compensating in some ways for loss of soil fertility, is toxic to many soil organisms and causes soil biological health to decline. 33 soil fertility + + crop health - R Chem Rescue pesticide use Chem Welfare/Warfare soil biological soluble salt health fertilizer use R Anyone want to try this one? 34 soil fertility + + crop health - R Chem Rescue pesticide use Chem Welfare/Warfare soil biological soluble salt health fertilizer use R According to Karlo . chemical warfare, in combination with the nutrient imbalances typical of conventional fertilization and increased pest vulnerability of large scale, genetically homogeneous monoculture, weakens crop health. To compensate, farmers increase pesticide rescue therapy. Rising pesticide toxicity causes further damage to the health of the soil community. 35 soil fertility + + crop health - R Chem Rescue pesticide use Chem Welfare/Warfare soil biological soluble salt health fertilizer use + R R + compaction Tilth Factor 1 - soil tilth Then what happens? We have a third reinforcing loop here now! 36 soil fertility + + crop health - R Chem Rescue pesticide use Chem Welfare/Warfare soil biological soluble salt health fertilizer use + R R + compaction Tilth Factor 1 - soil tilth According to Karlo some chemical fertilizers increase soil compaction, which weakens the soil community and crops even more. 37 - <a href="/keyword/soil-organic-matter/" >soil organic matter</a> tillage soil fertility + + crop health - + tractor passes R Chem Rescue R Chem Welfare/Warfare pesticide use - soluble salt fertilizer use - soil biological health + R + - compaction + Tilth Factor 1 - soil tilth And then? 38 - <a href="/keyword/soil-organic-matter/" >soil organic matter</a> tillage soil fertility + + crop health - + tractor passes R Chem Rescue R Chem Welfare/Warfare pesticide use - soluble salt fertilizer use - soil biological health + R + - compaction + Tilth Factor 1 - soil tilth Karlo states that the heavy tillage associated with annual row cropping can relieve compaction (temporarily), but increases the number of tractor passes, which increases compaction. Tillage also depletes <a href="/keyword/soil-organic-matter/" >soil organic matter</a> . 39 <a href="/keyword/soil-organic-matter/" >soil organic matter</a> tillage soil fertility + + crop health - + tractor passes R Chem Rescue pesticide use Chem Welfare/Warfare soil biological + soluble salt health fertilizer use + R water cycle health + R + + - compaction Tilth Factor 1 R Tilth Factor 2 - soil tilth So, what next? 40 <a href="/keyword/soil-organic-matter/" >soil organic matter</a> tillage soil fertility + + crop health - + tractor passes R Chem Rescue pesticide use Chem Welfare/Warfare soil biological + soluble salt health fertilizer use + R water cycle health + R + + - compaction Tilth Factor 1 R Tilth Factor 2 - soil tilth Poor soil tilth due to compaction reduces the ability of the soil to hold the water needed by crops and the soil community. 41 <a href="/keyword/soil-organic-matter/" >soil organic matter</a> - R tillage Chem Replacement soil fertility + + crop health - + tractor passes R Chem Rescue pesticide use Chem + Welfare/Warfare soil biological + soluble salt health fertilizer use + R water cycle health + R + + - compaction Tilth Factor 1 R Tilth Factor 2 - soil tilth Now what? 42 <a href="/keyword/soil-organic-matter/" >soil organic matter</a> - R tillage Chem Replacement soil fertility + + crop health - + tractor passes R Chem Rescue pesticide use Chem + Welfare/Warfare soil biological + soluble salt health fertilizer use + R water cycle health + R + + - compaction Tilth Factor 1 R Tilth Factor 2 - soil tilth Well Karlo believes as farmers depend increasingly on conventional fertilizers, they neglect to maintain <a href="/keyword/soil-organic-matter/" >soil organic matter</a> , which diminishes soil biological health and fertility. 43 Conventional Agriculture: A Slow Moving Disaster <a href="/keyword/soil-organic-matter/" >soil organic matter</a> - R tillage Chem Replacement soil fertility + + tractor passes + crop health R - Chem Rescue pesticide use Chem Welfare/Warfare soil biological + soluble salt health + fertilizer use + R water cycle health + R + + - compaction R Tilth Factor 2 Tilth Factor 1 - soil tilth + Get it? 44 Thinking About Sustainability Conventional nutrient management models focus on levels of water-soluble forms of plant nutrients (chemical fertilizers) such as nitrates and phosphates. According to Karlo such an approach constitutes a simplistic mental model of the agroecosystem - that overlooks the key role of <a href="/keyword/soil-organic-matter/" >soil organic matter</a> levels and trends over time as they affect nutrient availability, overall system health, and farm productivity. 45 In temperate, moderate rainfall climates like the Northeastern US where <a href="/keyword/soil-organic-matter/" >soil organic matter</a> can accumulate, building organic matter has proven to increase overall agroecosystem health and resilience, and long term farm productivity. So 46 We need to test a model of an agroecosystem with ...