Crop Diversification for an Agroecological Transition

Keynote by Damien Beillouin UPR HortSys, PerSyst – CIRAD

2025-06-17

Act I — Food systems on a Burning Planet 🌍🔥

“We are the first generation to feel the effects of climate change — and the last that can do something about it.”
— Barack Obama - 2015

  • Food systems are the main driver behind 5 of the 6 planetary boundary breaches

  • The food system alone is responsible for:

    • 30% of GHG emissions,
    • 70% of freshwater use,
    • 80% of deforestation,
    • Massive biodiversity loss.
    • Food system change is vital to achieve 1.5°C, beyond fossil fuel shifts.
    • Diets change could prevent up to 15 million deaths per year.


➤ Food systems must not just feed — it must regenerate.

Planetary Boundaries

Campbell, B. M., et al. 2017. Ecology and Society
doi.org/10.5751/ES-09595-220408

🌴 Tropics at the Heart of Planetary Overshoot


Planetary Boundary Safe Limit Current Global Level Tropics Systemic Impact
🌳 Land-System Change ≥ 85% forest intact ~60% forest cover remains Tropical forest cover: America 84%, Africa 54%, Asia 37% CO₂ sink loss, water cycle disruption, biodiversity loss
🌍 Climate Change CO₂ ≤ 350 ppm ~417 ppm Net emitter: –1 PgC/year (Gatti et al. 2021) Amplifies global warming
🐾 Biosphere Integrity ≤ 10 extinctions/MSY > 100 ext./MSY Tropics = bulk of extinction pressure Ecosystem collapse, loss of habitats
💧 Freshwater Change ≤ 10% blue water use ~18% global withdrawal Tropics: rising evapotranspiration pressure Local & global climate disruption


🌎 Protecting tropical systems is not just local policy — it’s global climate defense.

Act II — Agriculture: Driver of Planetary Boundary Breaches or Key to Their Repair? 🌾 ♻️

Current state of crop diversity : specialize, intensify, simplify — and you’ll feed the world

-> Four species — wheat, rice, maize, and soybean — = 50% of cropland (Renard & Tilman, 2019, Nature).

-> The number of farms is projected to decline by 55% by 2100 (Mehrabi et al., 2023, Nat. Sust).

Current level of crop diversity

Merlos et Hijmans, 2022. Env. Res. let.
doi.org/10.1088/1748-9326/ac62ab

Crop Diversity Gaps

-> The potential of diversity remains largely underutilized


Current level of crop diversity gaps

Merlos et Hijmans, 2022. Env. Res. let.
doi.org/10.1088/1748-9326/ac62ab

“We are producing more food than ever, but at the expense of our future.”
— FAO, 2020

Diversity as a Solution, Not Nostalgia ? 🌱🌾🌽🌻

“Nature’s secret is diversity. Why would agriculture be any different?”

Crop diversification includes practices that increase crop variety and system complexity across time and space (Kremen et al., 2012):

  • Intercropping: growing multiple crops simultaneously
  • Agroforestry: integrating trees with crops and/or livestock
  • Crop rotations: sequential planting of different crops on the same land
  • Cover crops: plants grown to protect and enrich soil between main crops
  • Variety mixtures: multiple crop genotypes cultivated within fields
  • Landscape diversity: integration of semi-natural habitats

These practices can be combined or layered within the same system, creating diverse agroecosystems adapted to local contexts.

Diversified system

Diversified system with fruits and vegetables.

The Challenge of Measuring Complexity 🧩🌍

“The more diverse the system, the harder it is to capture its full value.”


Assessing crop diversification isn’t straightforward:

  • Too many forms: rotations, intercropping, agroforestry, cover crops, and more…
  • Too many studies: over 35 000 primary studies, 200 meta-analyses, each with its own scope and focus
  • Too much context-dependence: results vary widely by soil, climate, crop type, and management practices


🧠 To address this complexity, we adopted a two-step approach:

  1. Broad perspective: a second-order meta-analysis to reveal global patterns across fragmented evidence.
  2. Focused perspective: first-order meta-analyses to understand contextual nuances and variability.

Schema_2MA

Meta-of-meta: connecting the dots across hundreds of studies.

Broad perspective

🌾 Diversification Works — And the Numbers Prove It

Diversified cropping systems often outperform simplified ones — for nature, for climate, and for food production

GCB_Results

Beillouin et al., 2021. Global Change Biology.
doi.org/10.1111/gcb.15747

🌾 Diversification as a Strategy — What Works Best?

Diversified cropping systems are not all equal.

Results_Global_change_Biology2

Beillouin et al., 2021. Global Change Biology.
doi.org/10.1111/gcb.15747

🌿 How Does Crop Diversification Compare to Other Farming Strategies? - CARBON

Not all agricultural practices perform equally.
Crop diversification — including agroforestry — stands out as one of the most effective strategies
for improving ecosystem services and long-term sustainability.

MA_Carbon

Beillouin et al., 2021. Global Change Biology.
doi.org/10.1111/gcb.15747

🌿 How Does Crop Diversification Compare to Other Farming Strategies? - BIODIVERSITY

Not all agricultural practices perform equally.
Crop diversification — including agroforestry — stands out as one of the most effective strategies
for improving ecosystem services and long-term sustainability.

MA_Biodiv

Beillouin et al., in prep. .
doi.org/XXX

Focused perspective

What Shapes the Success of Diversified Cropping Systems? (1)

Effect of legume-based rotations on crop yield (global scale)

Effect of agroforestry on SOC (LAC countries)

detailled study

Zhao et al., 2022. Nat. Comm.
doi.org/10.1038/s41467-022-32464-0

Beillouin et al., XXX. in Prep
doi.org/XXXX

What Shapes the Success of Diversified Cropping Systems? (2)

Effect of legume-based rotations on crop yield (global scale)

Effect of agroforestry on SOC (LAC countries)

detailled study

Zhao et al., 2022. Nat. Comm.
doi.org/10.1038/s41467-022-32464-0

Beillouin et al., XXX. in Prep
doi.org/XXXX

What Shapes the Success of Diversified Cropping Systems? (3)

Landscape_effect

Sanchez et al., 2022. AGEE.
doi.org/10.1016/j.agee.2022.107933

What Shapes the Success of Diversified Cropping Systems? (4)

YANG_CA

Su et al., 2021. Sc. reports.
doi.org/10.1038/s41598-021-82375-13

Act III — So Why Isn’t Everyone Doing It? 🚧

Despite all the evidence, diversified systems remain rare. (Tscharntke et al., 2012)


Technical Barriers

  • Knowledge gaps persist, with much research focused on individual practices rather than holistic system combinations and trade-offs (Beillouin et al., 2021)


Structural Obstacles

  • Subsidies overwhelmingly favor monocultures (Anderson et al., 2023)
  • Research and extension locked into input-intensive paradigms (Pretty, 2008)
  • Market chains reward uniformity, not resilience (Gliessman, 2015)
  • Complex socio-economic and institutional factors shape adoption decisions (Sánchez Bogado et al., 2024)

“The problem isn’t knowledge. It’s power, narratives, and institutions.” (Perfecto & Vandermeer, 2010)

Technical Barriers

Technical Barriers: Still Emerging Evidence

K_Gap

Beillouin et al., 2019. Data in brief.
doi.org/10.1016/j.dib.2019.103898

What Species Are We Talking About?

Species_Gap

Beillouin et al., 2019. Env. Res. let..
doi.org/10.1088/1748-9326/ab4449

Blind Spots on the Global Map

Map_divers

Beillouin et al., 2021. Glob. chane Biology.
doi.org/10.1111/gcb.15747

Structural Obstacles

Complex socio-economic and institutional factors

Sanchez_abstract

Sanchez et al., 2024. Global Food Security.
doi.org/10.1016/j.gfs.2024.100820

Act IV — 🚀 What Research Fronts to Unlock the Transition?

🧩 1. Landscape Design: How to Structure Diversification?

  • Ecosystem services emerge beyond the plot: we need to design functional mosaics.
  • Which configurations deliver the most? 20% semi-natural habitat? Strategic patches?
  • Go beyond land sparing vs. sharing: focus on multi-functionality and spatial synergies. (Balmford et al., 2025 vs. Kremen et al.)

landscape_scenarios

Frederick Gerits.

🧪 2. Complex Systems: What Works, in What Combination?

  • Most trials test one practice — but real farms mix: agroforestry + cover + reduced tillage…
  • Long-term trials are rare. But we can use observational data smartly:
    → Surveys + Matching, combining diverse datasets
    → Detect patterns of success from messy, real-world data.

combo_practices

Guard-Lavastre-CIRAD.

⚖️ 3. Trade-Offs & Indirect Effects: Are We Capturing the Full Picture?

  • Yield vs. biodiversity? Income vs. resilience?
    → Too many studies still focus on a single outcome.
  • Effects can be delayed, non-linear, indirect.
    → We need models that connect soil → function → decisions over time.

tradeoffs_indirects

Balmford et al., 2025. Science.
https://eprints.whiterose.ac.uk/id/eprint/223903/

🌍 Act V — A Just and Urgent Transition

🌍 Agriculture as a Transformative Lever

  • Agricultural practices are not just part of the problem — they are a powerful lever for climate, health, and equity.
  • Even with a clean energy transition, we won’t meet global goals without transforming how we farm, eat, and manage land.
  • No single fix will be enough. We need bundles of actions: agroecological practices, dietary shifts, reduced waste, and social justice.
  • The challenge is massive — but so is the opportunity (EAT Lancet, 2025):
    → Healthy diets could prevent 15 million deaths/year
    → Sustainable farming could make food systems net carbon-negative.
    → Fairer food systems could restore dignity, resilience, and ecological integrity.

Damien Beillouin – CIRAD | Agroecology & Crop Diversification