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Basche swcs 7.31.17_final

  1. 1. Can ecological practices mitigate floods and droughts? Pairing meta-analysis with a hydrology model to understand soil water impacts Andrea Basche Research Fellow SWCS Annual Meeting July 31, 2017
  2. 2. UCS Happy Hour & Upcoming Report • 5:30pm-7:30pm TONIGHT! at The Great Dane • Learn more about upcoming floods and droughts report AND how to stay connected to our Science Network resources
  3. 3. Scattered Trees Forest Prairie Water/Wetland Historic Vegetation of Iowa 1832-1859 Source: Iowa State University Iowa Dept. of Natural Resources Basche and Edelson. 2017. Agroecology and Sustainable Food Systems.
  4. 4. Basche and Edelson. 2017. Agroecology and Sustainable Food Systems.
  5. 5. 45% 7% Basche and Edelson. 2017. Agroecology and Sustainable Food Systems.
  6. 6. Healthy soils could lead to better water outcomes, yet questions remain • What do soil improvements actually mean for water impacts on a field scale? • What practices are most effective and in what environments? • How do conservation practices change water outcomes on a landscape scale?
  7. 7. No-TillCropland Grazing Cover Crops Perennials Perennial grasses, Agroforestry, Forestry Crop Rotation Grazing Management Reduced rates, Rotational grazing, Grazing exclusion Meta-analysis How do agricultural practices in crop & grazing lands impact infiltration rates on individual fields? 7 studies 52 studies 11 studies 23 studies 37 studies 8 studies 24 205 39 81 221 40 Number of paired observations Basche and DeLonge. Under Review; DeLonge and Basche. Under Review.
  8. 8. No-TillCropland Grazing Cover Crops PerennialsCrop Rotation Grazing Management Meta-analysis 7 studies 52 studies 11 studies 23 studies 37 studies 8 studies TREATMENT Conventional or Reduced Tillage Crops Only No cover crop Annual Crop System Mono- culture Conventional or Continuous Grazing CONTROL How do agricultural practices in crop & grazing lands impact infiltration rates on individual fields?
  9. 9. No-TillCropland Grazing Cover Crops PerennialsCrop Rotation Grazing Management Meta-analysis Average infiltration rate improvement -21% +6% +19% +35% +59% +59% 7 studies 52 studies 11 studies 23 studies 37 studies 8 studies Basche and DeLonge. Under Review; DeLonge and Basche. Under Review.
  10. 10. How do continuous living cover practices impact water storage on individual fields? Porosity Upper end of plant available water Mean increase of 8-9% for 27 studies analyzed Only evaluated continuous living cover practices: cover crops, perennial crops and agroforestry Basche and DeLonge. In Press. Soil Science Society of America Journal.
  11. 11. Diverse cover crops Perennial crops (i.e. alfalfa) Livestock on perennial grassesHow do agricultural practices in crop & grazing lands impact water on a landscape scale?
  12. 12. Livestock on perennial grasses Improving water outcomes with better soil water storage capacity and more diverse crop management Diverse cover crops Perennial crops (i.e. alfalfa)
  13. 13. Livestock on perennial grasses Basin Characterization Model Diverse cover crops Perennial crops (i.e. alfalfa)
  14. 14. Perennial grasses in areas with >5 tons/acre/yr soil loss Cover crop added to areas with >2 tons/acre/year soil loss Daily Erosion Project Modeling, Iowa State University. Cruse et al. 2006. Daily estimates of rainfall, water runoff, and soil erosion in Iowa. Journal of Soil and Water Conservation..
  15. 15. Perennial grasses in areas with ~$80 ha/yr loss Cover crop added to areas with <$50 ha/yr profit Brandes et. al. 2016. Subfield profitability analysis reveals an economic case for cropland diversification. Environmental Research Letters.
  16. 16. Livestock on perennial grasses Diverse cover crops Perennial crops (i.e. alfalfa) • 10-14% less runoff overall • 7-10% more water use from plants overall • In severe droughts (1988, 2012) up to 16% greater crop water use • Similar magnitude benefits with future climate
  17. 17. Cedar Rapids • 22% perennials • 27% including cover crop • 17% reduction in flood frequency • 13% less runoff • 8% more crop water use X% of Least Profitable Corn/Soy Acreage Shifted to: Creates Benefits of:
  18. 18. Profitability Scenario: Runoff Reduction
  19. 19. Erosion Scenario: Actual Evapotranspiration
  20. 20. Summary • Conservation practices have clear benefits for water infiltration and water storage on field and landscape scales • Largest benefits come from continuous living cover • Targeting regions of lower profitability or greater erosion potential to include perennials or cover crops to build healthier soil improves water use efficiency in wetter and drier years
  21. 21. UCS Happy Hour & Upcoming Report • 5:30pm-7:30pm TONIGHT! at The Great Dane • Learn more about upcoming floods and droughts report AND how to stay connected to our Science Network resources
  22. 22. Thank You
  23. 23. Analysis Details • For each study, extract key data: – Infiltration rate with & without conservation practices – # treatment replications – location – annual rainfall – soil type • Calculate “Response Ratio” – Ratio of infiltration rate of experimental treatment / the control treatment • Statistics – mixed-effect models – take into account effect of study Basche and DeLonge. Under Review; DeLonge and Basche. Under Review.
  24. 24. No-TillCropland Grazing Cover Crops PerennialsCrop Rotation Grazing Management Meta-analysis 7 studies 52 studies 11 studies 23 studies 37 studies 8 studies Infiltration rate improvements greater than one inch/hour (conservation – control) 21% 31% 22% 37% 42% 53% Percent of experiments that showed this large improvement:
  25. 25. Wang et al. 2015 Wang et al. 2015 LRR > 1 3-5x IR increase Perennial Experiments
  26. 26. Basche and DeLonge. Under Review; DeLonge and Basche. Under Review.
  27. 27. Brandes et. al 2016 Subfield profitability analysis reveals an economic case for cropland diversification. Environmental Research Letters
  28. 28. Percent [%] increase in Infiltration Rate (with Conservation Practice) No-Till Grazing Exclusion Grazing Management Cover Crop Perennials Crop Rotation Crop & Livestock NO CHANGE # observations
  29. 29. How do continuous living cover practices impact water storage on individual fields?
  30. 30. How do continuous living cover practices impact water storage on individual fields?
  31. 31. Erosion Scenario: Runoff Reduction
  32. 32. Profitability Scenario: Actual Evapotranspiration
  33. 33. No-Till Experiments
  34. 34. No-Till Experiments
  35. 35. No-Till Experiments
  36. 36. No-Till Experiments
  37. 37. Cover Crop Experiments

Notas del editor

  • Going to talk to everyone today about the work I’ve done for about the last two years as part of my fellowship w/ UCS
    This is all a part of a series of papers that are published or under review, and a part of a UCS report upcoming

    Increased rainfall variability is well documented in the historic record and is predicted to intensify with future climate change. Managing both excess water in periods of heavy rain and lack of water in periods of inadequate precipitation will continue to be a challenge. Improving soil resiliency through increased water storage is a promising strategy to combat effects of both floods and droughts. The goal of this research is to quantify to what extent conservation and ecological practices can improve key indicators of soil hydrology on both a field and landscape scale. A meta-analysis project including approximately 130 studies of field experiments evaluated the impact of various conservation practices, ranging from no-till to the inclusion of perennial crops to improved livestock grazing management. This analysis found that on average that these changes to agricultural management significantly improved water infiltration rates. In particular, when perennial practices were compared to annual practices, half of the experiments analyzed increased infiltration rates to those greater than a two inch rainfall event, dramatically increasing the soil’s ability in those locations to absorb rainfall during extreme events. This meta-analysis further found that practices which promote continuous living cover (including perennial grasses, agroforestry and cover crops) increased soil porosity and the water retained at field capacity by 4-15%. A novel modeling experiment is evaluating how these improvements in soil hydrology would translate into water savings on a regional scale using a case study in the state of Iowa. Results will be presented from both the meta-analysis and hydrology modeling research to better quantify how field scale soil improvements translate into landscape scale water benefits, including reduced runoff in wet years and increased soil water storage in dry years.
  • Describe where the Great Dane is
  • The reality of water risks is probably not new to anyone here – this is data from the NCA depicting growing rainfall variability
    This is showing the change in the Heaviest one percent of rainfall days compared to the beginning of the 20th century – increasing across the US – but the most so in the MW and NE – here the MW +37% in MW and even higher in NE +71%

  • And this has impacts for ag community of course – a screengrab here of a piece from last year, 2016, which would be five years from the 2011 flooding on the Missouri river where farmers are still feeling the effects
  • Impacts the urban environment as well – when you have very heavy rain here falling at higher rates
    That is perfectly consistent with a warming atmosphere
    SO I’ve been happily on vacation the last week but this is from Yesterday – last week there was a very unusual amount of rain in the beltway– six eight inches in some areas – here one record of 3 inches in 45 mins. Serious deluges

    So this increase in rainfall variability has real impacts in urban and rural environments – and at the same time this is happening
  • You have agricultural landscapes that are changing also – no better place than Iowa to look at this
    In the mid 1800s the land was perennially based – predominantly prairie and forests – so plants using water all year

  • To where we are today which is probably familiar for lots of the folks from the Midwest – yellow is corn, green is soy

    68% of land cover is agriculture and of those harvested acres – 90+% is in two crops that only use water for a few months of the year
  • Just taking a closer look at how crop mix has changed since WWII
    Data from many ag census – black symbols are corn or soy – summer annual crops that only grow and use water part of the year
    Open symbols are those that grow throughout the year like hay or alfalfa, or in fall and spring like oats and barley
    So even pre WWII you had a healthier mix in Iowa of crops that grow throughout the year – making up 45% of crops planted
    Now its 7% - variety of economic and technological factors that have contributed to this
    So we have agricultural landscapes that are in large part annual crop based – and growing rainfall variability – what are ways to manage this?

    I’m looking at soil’s ability to take on and hold water.
    Why does that matter.
    Some have to do with farming and age old challenges of flood and drought resilience
    Some has to do with the change that’s coming w/ more intense rainfall and longer stretches of dry
    Third that is a huge issue in ag communities, when there is flooding there is more pollution going into water bodies

  • One opportunity with a lot of promise is making the soil more sponge like – more able to hold on to water in heavy rainfall to lessen flood impacts and then to have it for periods of less rainfall
    SO I suspect all of you have seen this before - very interesting – more carbon more water – healthier soils are better for responding to rainfall variability and helping deal with these issues
  • All well and good if that’s the case but do we really understand the contribution soil can make to reducing impacts of rainfall variability

    Questions such as: what does this mean in a drought – how much more water can plants use? Or with a heavy rain event – how much more water can be absorbed in a heavy rain event?

    And what agricultural management might help get us there??

    Or if you had better soils across the landscape what does it mean?

    So those questions are what I’ve been trying to answer – going to walk you through some of what I’ve learned in attempting to answer these – which could probably take up the rest of my career
  • SO one of the questions I’ve asked was in regards to infiltration rate because that is so fundamental to water staying in the soil – step one really to this idea of making the soil more sponge like

    CLICK: To answer this question I’ve been working on a MA- a quantitative synthesis of published studies –- MA is a very powerful methodology bc it shows for you the combined effect of many different experiments

    And we wanted to look at a range of different common conservation and diversified practices as you see here – compared to more conventional practices as a control

    And I want to show you first the number of studies we’ve found for each practice. Some things are more frequently studied than others – another useful aspect of an analysis like this

    Also going to show you the number of paired comparisons within each of the practices – because some experiments look at tillage and cover crops so that becomes multiple data points – that’s part of the nitty gritty of what is happening

    In total this equals >400 observations and >120 studies across all continents minus antarctica

  • Here are the control treatments, so different controls
    So no tilled we’ve compared to CT or RT
    Perennials compared to annual crop systems
  • Just want to show the overview average for all of the practices that we looked at so the numbers I’ll show are the

    Baseline improved averaged across all of the experiments that fell within the categories – mean percent increase is what you see below each of these practices

    We’ve found very significant differences between the improvement in IR between these practices – where the clear largest improvements come from perennial crops compared to annual controls, from improvements to grazing/grasslands lands such as reduced numbers of animals or more rotational/complex management, and to cover crops

    RED – those where error bars are sig different from zero

    Can answer more questions if folks are interested in details – done a thorough analysis of each of the categories – we find that no-till experiments in wetter environments led to IR increases, and NT + residue retention led to sig increases, etc.

  • So in addition to IR, We also asked a question about some specific soil water properties related to water storage – and zoomed into the CLC practices
    Porosity or pore space in the soil – higher number is greater sponge like capacity
    Upper end of plant available water or FC
    Found 27 studies that fit criteria when focused just on CC, perennials and AF
    What you see on the x axis is the percent change compared treatment to control – the distribution fo all the data points – triangles for porosity and circles for FC – a range of -20 to +40% with a mean of 8-9% and a 95% CI of ~4-14%
    Not as large a numbers as IR but really solid for these different properties – this is up on the SSSAJ first look page if anyone’s interested
  • Ok so that’s what we’ve learned from individual field experiments and the MA. Now transitioning into the work we’ve done to answer questions about healthier soil impacts on a landscape scale:

    Let’s try to envision an agricultural landscape with more diverse crops – more practices that promote perennial crops growing all year long such as increasing perennial grasses for grazing animals, and more cover crops – because we know based on the MA that these practices were the ones that consistently improved water entry to the soil and water storage

  • Such that with those crop changes we make modest, achievable improvements to the soil as I just described from the meta-analysis – which we’ve found to be evident on a field scale

    What does that mean on a landscape scale?

  • SO to try to represent this, we’re working with a hydrology model to represent the state of Iowa – called the BCM - developed by Lorrie and Alan Flint USGS scientists in Sacramento who’ve used the tool to look at water availability in future of California – The central part of the model’s ability to calculate the ins and outs of the water balance is the soil profile. CLICK– predicts variables such as actual water use from the plants, and runoff that would be a proxy for flood impact

    And we’re able to manipulate the FC & porosity – properties related to storage that again we know can realistically be improved through more diverse management, and assuming that across the landscape there are more cover crops & perennial crops using water at different times of the year

    so we’re working as best we can with that tool trying to alter vegetation and soil to best represent what those realistic improvements that I just showed you- and to better understand what this means on a landscape scale?

  • So then the next question would be – WHERE might we target some of these crop and soil improvements:

    I’ve looked at two scenarios of crop and soil change the first is assuming we shifted the most erodible areas – anything greater than 2 tons per acre per year
    Best science says that soil replacement rates are ~0.5 ton/acre/year

    CONVERTING THE ~30-40% MOST ERODIBLE AREAS to perennial grasses or corn/soy with a cover crop – so basically what this assumes is a more even distribution of water use throughout the year AND improved soils based on what we found for cover crops and perennials
    Based on the modeling work of DEP out of ISU
  • The second is CONVERTING THE ~30-40% LEAST PROFITABLE areas similarly to cover crops and perennial grasses
    Looks a little different a little more patchwork –based on the work also of ISU scientists - Elke Brandes first author – they’ve integrated crop yields, soil types, commodity prices, input costs, cash rents etc.

    So we’ve looked at 17 different watersheds that span essentially the whole state of Iowa, and the historic simulation runs from 1981-2015
  • Just want to give you a sense of the overall trends when averaged across historical period of 1981-2015 AND the different watersheds which more or else comprised the entire state
    General patterns here in terms of sizable reductions in runoff AND in plant water use
    Also more water use in drought years
    Also run the same three land use scenarios and seem similar magnitude benefits in a significantly hotter and slightly wetter future climate

  • Now just want to take a closer look at what this means for an individual watershed – this is the cedar river basin – draining into the metro area of cedar rapids, 2nd largest city in IA had a multi billion dollar flood event in 2008 – this is an area that is no stranger to flooding

    Just using the profitability scenario here – what this shook out to in this watershed was shift in the 22% least profitable corn/soy areas to perennials, and another 27% to include cover crops – more patchwork with some emphasis on the riparian areas

    Actually reduces the number of months that reach flood stage by 17%
    13% less runoff and 8% more crop water use actual ET

    21.9% CS shifted to perennials
    26.5% shifted to include cover crop
    Flood reduction of 17% (4 less months but could describe what this means)
    13% change in runoff, 8% increase in AET
  • Just want to show two more quick graphs if I haven’t bored you enough with graphs –
    This is demonstrating the average precent change in runoff overall all the basins we modeled and graphed by annual precip
    Showed the overall percent reduction in runoff – here I’m showing how that varies by rainfall year
    Interestingly, the runoff reduction is actually HIGHER in dry years
    So what this means from an efficiency standpoint – is that those three inch rains that happen in dry years are more efficiently captured by the soil
  • AND from the crop water use standpoint a similar pattern, that the more rainfall there is the greater the increase in AET
    Again the diversified crop / healthier soil scenario is more efficient at using the additional water in wetter years
  • And to wrap up – this whole project was an exercise to get our arms around how much the soil can contribute to reducing impacts of rainfall variability

    That these practices can improve water outcomes on field and landscape scale
    Specifically CLC or suites of practices
    In wetter and drier years this works to improve efficiency

    I see this work as proof of concept that this ecological approach to flood and drought impact mitigation has a lot of potential and deserves more attention
    .So that’s Just one piece of the puzzle – other approaches to risk management

  • Describe where the Great Dane is
  • And remember when we think back to the way intense precipitation is increasing and how our agricultural regions are becoming more simplified
    Critical research if we’re going to solve the concurrent problems related to rainfall variability
    We can tackle this through better ecological practices – can save money on irrigation, fertilizer – can keep more runoff out of waterways – multiple wins wins with this type of approach

  • Just to show a few more specifics again about the methods here and explain the response ratio so you have a sense of what you’re looking at
    Response ratio is the ratio of the exp to the control
    So if this is above one – the cons practice increased IR if it is negative it decreased IR
    Group the RR together to look for patterns – across different practices, envrionments, etc.
  • Another metric we looked at was ACTUAL amt of water increase
    If you subtract reported rate in the exp trt minus the control then you can understand the increase in lets say the absorption capacity of the soil – how much more sponge like is the soil in that expt as a result of the conservation practice in context of an actual heavy rain event

    Here I decided to use a threshold of a one inch rain event – and so the numbers I’m showing here are the % of the expts in each category that lead not only to an increase in IR but also to an increase that is >1inch/hr
    That’s big! So even though mean increases in baseline were low in NT, 1/3 of expts or so had big improvements. AND for perennials, 2/3 led to large improvements. So an interesting dataset to look at some of these patterns as they relate to heavy rainfall

    So if we define a threshold of heavy rainfall at 1 inch/hour – hard to find a clear definition of what is “heavy” rainfall because that’s very region specific so if we assume 1 inch/hour- it’s easy to calculate the absolute difference in the reported IR between the alternative practice and the conventional control

    These numbers represent the percentage of observations within each practice that did indeed increase IR and to a rate above 1 inch/hr

    So what this is saying is that if we want to INCREASE IR – absorption capacity – above a threshold like 1 inch per hour – here is what the frequency of that increase is for different agricultural practices. that means that the soil is directly that much more able to soak up that heavy rain event in this percent of the experiments that are in the database

    This is a slightly different picture, that there are a number of studies that report such increases in IR for each practice – but again – the most consistent improvements coming in the covering the soil with living roots

    As one example of how this is different, the baseline improvement for NT is small/statistically insignificant but there are a number of experiments where the increase in IR is important, so I’m working on explaining some of this, in what environments are those increases the largest.

  • Want to show briefly the increase in IR w/ in the perennial category bc this was the largest magnitude increase
    And also how the three diff categories that we included compared
    16 paired observations (out of 34! Wow!) were agroforestry – but here the mag in many studies was huge – up to 400% increases

    Chirwa et al. 2003, Zambia: Improved fallow with trees
    Wang et al. 2015, China: Alley cropping walnut and wheat
    Ketema and Yimer 2014, Ethiopia: Silvopasture
    Bharati et al. 2003, Iowa: Agroforestry riparian buffer
  • This is based on the work of ISU scientists where they’ve used crop yields, input costs, commodity prices, CSR which is an indicator of soil type and they demonstrate that in some years profitability across large parts of the state are actually well in the red or below zero

    So used those two geographic analyses to say – if we converted the 50% most erodible or 50% least profitable cropped areas – improving soils and changing crops - what would that do for water outcomes
  • Here is the same data broken out in graph form with error bars - Make sure to orient to what folks are looking at
    No change would be an average effect of zero
    These are the means that you just saw in addition to the 95% confidence intervals, so we consider an effect to be significant if the error bars don’t cross zero

  • Here is porosity broken out by category
    The values on the side are the paired comparisons / studies
    So a smaller dataset but interesting and similar positive effects

    Agroforestry studies:
    -Nyamdzawo et al. 2012 (Zimbabwe): improved fallow with trees, control- continuous corn
    -Silva et al. 2011 (Brazil): Silvopasture, control- corn-soybean
  • Here is this broken out for the upper end of plant available water
    So the most expts here looking at CC and perennials but neat to see that AF continues to show solid increases on these properties also
    So the second part of the MA work looked at some very specific properties around water storage, and on to another very important question about the landscape scale changes

    Agroforestry studies:
    -Nyamdzawo et al. 2012 (Zimbabwe): improved fallow with trees, control- continuous corn
    -Silva et al. 2011 (Brazil): Silvopasture, control- corn-soybean
  • Want to just dive a little deeper into the NT comparisons, something that obviously has been studied a lot and is very important
    Clear that NT can have an effect in different environments
    So this is the same style graph but only for NT – again above zero is a sig positive effect – and the number of response ratios/paired observations
    When we grouped the database by soil texture its hard to see a real clear effect

  • Also difficult to detect a clear effect of time! We thought the longer the treatment was in place there’d be a larger increase in IR

  • Here’s something clear – looks like the regions with less rainfall are pulling down the average – could suggest that NT is more effective in wetter areas for IR

  • Also interesting to see where experiments reported and broke out IR reporting when crop residue was retained or not – so this would suggest that when NT was used in coordination with residue retention there was a clearer pos effect in IR

  • And on that note just one quick slide to show the same graph for cover crops
    Really dove deep into these groups because there were just more response ratios to compare
    Here – when experiments had a cover crop and were also NT then we saw a larger increase in IR
    Those two findings together may indicate a more clear effect of suties of practices together - NT+CC, NT + res retention