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"Is Aquaculture Really an Option? A Theoretical Analysis" - “Phân thích lí thuyết: Nuôi trồng thủy sản có thực sự là một lựa chọn?”

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Giáo sư Katheline Schubert tham gia VEAM 2015 với bài trình bày “Phân thích lí thuyết: Nuôi trồng thủy sản có thực sự là một lựa chọn?”.
Professor Katheline Schubert joined in VEAM 2015 with the presentation “Is Aquaculture Really an Option? A Theoretical Analysis”.

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"Is Aquaculture Really an Option? A Theoretical Analysis" - “Phân thích lí thuyết: Nuôi trồng thủy sản có thực sự là một lựa chọn?”

  1. 1. Is Aquaculture Really an Option? A Theoretical Analysis Esther Regnier & Katheline Schubert Paris School of Economics, University Paris 1 Panthéon-Sorbonne VEAM 2015 E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 1 / 30
  2. 2. Introduction While breeding of terrestrial animals was implemented about 8 000 years ago and substituted to hunting rapidly, it took us a very long time to repeat the experience with …sh. Aquaculture exists in many parts of the world since the Middle Ages but did not replace …shing until now. Population growth and increase in standards of living in developing countries =) growing demand for animal protein. However, increase of breeding limited by land use con‡icts, and the maximum capture …shery potential from world’s oceans has been reached: 61% of world assessed marine …sh stocks are fully exploited, 30% are overexploited (FAO 2014). E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 2 / 30
  3. 3. Is aquaculture really an option? YES Annual average growth rate of aquaculture from 1970 to 2012: 8.6% (FAO 2014). Fastest growing food industry. Aquaculture provided 9% of world …sh production in 1980, 27% in 2000, 42% in 2012 (FAO 2014). The optimistic view is that aquaculture is going to replace at least partially open-sea …shing, helping to make …sheries sustainable, and providing food security for many developing countries. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 3 / 30
  4. 4. Is aquaculture really an option? NO The technology presents limitations in terms of environmental sustainability: inland and coastal farms cause the destruction of natural habitats; release of untreated water and feeces damages ecosystems (pathogen invasion); use of fertilizers =) euthrophication; aquaculture depends on low value wild …sh as an input. FIFO: number of tons of wild …sh necessary to produce 1 ton of farmed …sh. For carnivorous species (salmon) it may reach ' 5. Huge. Very ine¢ cient technology. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 4 / 30
  5. 5. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 5 / 30
  6. 6. Motivation Investigate the impact of aquaculture on …sh consumption, welfare and wild …sh stocks, taking into account: 1 its dependence on reduction …sheries; 2 consumer preferences; 3 biological interactions. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 6 / 30
  7. 7. Sketch of the model Stylized model including the demand side, an edible …sh …shery, a reduction …shery and aquaculture, where: …sheries are in open access; wild edible …sh and farmed …sh are strong substitutes; aquaculture harvests feed …sh to grow farmed …sh; the wild edible …sh feeds on the same stock. the more carnivorous the farmed …sh species, the more ine¢ cient its production technology.E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 7 / 30
  8. 8. The demand side Utility function of the representative consumer: U(Y1t , Y2t ) = [(1 α)Y 1 1 σ 1t + αY 1 1 σ 2t ]1/(1 1 σ ) Y1 / Y2: consumption of wild edible …sh / farmed …sh σ > 1: elasticity of substitution Partial equilibrium: consumers’total spending on …sh I exogenous and stationary Budget constraint: P1t Y1t + P2t Y2t = I 8t Demand functions: Y d 1t (P1t , P2t , I) and Y d 2t (P1t , P2t , I). E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 8 / 30
  9. 9. Biological interactions Biological interactions between the two wild species may exist or not (Peruvian anchovy and Norwegian farmed salmon). When they exist, they are of the predator-prey type. Species 1 (high-value edible species) is the predator, species 3 (a low-value pelagic species) the prey. Evolution of the 2 stocks: ˙X1t = F1(X1t , X3t ) ˙X3t = F3(X1t , X3t ) with F1(X1t , X3t ) = a1X1t b1X2 1t + d1X1t X3t F3(X1t , X3t ) = a3X3t b3X2 3t d3X1t X3t d1 0, d3 0; b1, b3 0; a1 0, a3 > 0. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 9 / 30
  10. 10. 4 possible long run steady states absent human intervention: 1 collapse of both populations; 2 collapse of population 1 only; 3 collapse of population 3 only; 4 coexistence of both populations. Condition of existence of SS 4: a1 b1 < a3 d3 Under this condition the unique stable SS is SS 4; otherwise, it is SS 3 =) this condition is supposed to be satis…ed. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 10 / 30
  11. 11. The baseline situation: capture …shery alone Harvest: Y1t = q1E1t X1t q1: catchability coe¢ cient; E1t : e¤ort. In open access e¤ort E1 adjusts to resource rent: ˙E1t = β (P1t Y1t cE1t ) Demand function: Y d 1t = I P1t Equilibrium of the wild …sh market at each date: Y1t = Y d 1 (P1t ). Eliminating P1 and Y1 yields: 8 < : ˙X1t = F1(X1t , X3t ) q1E1t X1t ˙E1t = β (I cE1t ) ˙X3t = F3(X1t , X3t ) E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 11 / 30
  12. 12. Again, 4 possible steady states: 1 collapse of both populations; 2 collapse of population 1 only; 3 collapse of population 3 only; 4 coexistence of both populations. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 12 / 30
  13. 13. SS 3 irrelevant by assumption (both species coexist absent human intervention; …shing the predator cannot worsen things for the prey). Condition of existence of SS 4: I < Iw (d1) = c q1 a1 + a3d1 b3 Iw : maximum revenue consumers can spend on …sh without inducing the extinction of the edible species. Increasing function of d1. When I < Iw (d1), the relevant SS is the interior SS 4; it is globally stable (stable node or a stable focus, depending on the parameters). Otherwise, species 1 collapses in the long run and the relevant SS is SS 2. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 13 / 30
  14. 14. The aquaculture sector and feed …shery Feed …shery (species 3): ˙X3t = F3(X1t , X3t ) Y3t ˙E3t = β [P3t Y3t cE3t ] Y3t = q3E3t X3t Aquaculture: farmers are in competition on the farmed …sh (species 2) market. Production function: Y2t = k(Y3t )γ , γ 2]0, 1[ k 2]0, kmax]: e¢ ciency of aquaculture in converting feed …sh into farmed …sh. The lower k the less e¢ cient aquaculture is (the higher the FIFO). E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 14 / 30
  15. 15. The coupling Prices adjust so that the 3 …sh markets are in equilibrium. Final dynamic system: 8 >>< >>: ˙X1t = F1(X1t , X3t ) q1E1t X1t ˙E1t = β [(1 At )I cE1t ] ˙X3t = F3(X1t , X3t ) q3E3t X3t ˙E3t = β [γAt I cE3t ] with At 1 At = α 1 α 1 σ k (q3E3t X3t )γ q1E1t X1t σ 1 σ where At 2 ]0, 1[ characterizes market interactions (it is a function of the price ratio). E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 15 / 30
  16. 16. Interior steady state Capture …shery + aquaculture Capture …shery alone bX1 = b3 Λ x1 + y1 bA X1 = b3 Λ x1 bE1 = I c (1 bA) E1 = I c bX3 = d3 Λ x3 + y3 bA X3 = d3 Λ x3 bE3 = γ I c bA bA = α 1 α k(q3 bE3 bX3) γ q1 bE1 bX1 σ 1 σ Λ = b1b3 + d1d3, x1 = a1 + a3d1 b3 q1I c , y1 = q1 d1 b3 γq3 I c , x3 = a1 a3b1 d3 q1I c , y3 = q1 + b1 d3 γq3 I c E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 16 / 30
  17. 17. Proposition A su¢ cient condition of existence of an interior steady state where wild …shing in open access and aquaculture coexist is: I < I := c a1 q1 + a3 γq3 Under this condition the interior steady state is unique. (ii) Absent biological interactions (d1 = d3 = 0), the unique interior steady state, when it exists, is globally stable; this remains true when biological interactions are moderate (su¢ cient conditions for stability are: d1 b3 q1 q3 , d3 b1 γ ). Besides, whatever the level of biological interactions, if consumer spending I is su¢ ciently small, the unique steady state is globally stable. (iii) If I I, when d1 d1 := b3 q1 γq3 , there is no interior steady state; but when d1 > d1 there may exist up to 2 interior steady states. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 17 / 30
  18. 18. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 18 / 30
  19. 19. To go further on stability, numerical simulations (assumption: d3/d1 remains the one of the reference calibration when d1 varies). Show that: in the region where there exist 2 SS, either both are unstable or one is unstable and the other stable, the stable one corresponding to the smaller bA. the interior SS may become unstable before or after I is reached; then simultaneous collapse of the 2 wild …sh stocks. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 19 / 30
  20. 20. Comparison with the baseline Proposition From an initial situation where the wild edible …shery is in open access, introducing aquaculture, with a wild feed …shery also in open access, leads in the long run to: (i) a smaller total e¤ort devoted to …shing; (ii) a higher stock of edible wild …sh and a lower price i¤ d1 < d1, and vice versa, and a lower feed …sh stock in all events; (iii) an ambiguous e¤ect on wild …sh consumption when d1 < d1, a decrease of wild …sh consumption when d1 > d1, and an ambiguous e¤ect on total …sh consumption in all events; (iv) a higher utility when d1 d1, but a possibly negative e¤ect on utility when d1 > d1. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 20 / 30
  21. 21. Moderate biological interactions: Strong biological interactions: d1 < d1 d1 > d1 bE1 + bE3 < E1 bE1 + bE3 < E1 bX1 > X1 bX1 < X1 bP1 < P1 bP1 > P1 bY1 ( > Y1 = 0 when Iw (d1) < I < I T Y1 otherwise bY1 < Y1 bU > U bU T U E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 21 / 30
  22. 22. Depending on the strength of biological interactions results change deeply. Moderate b.i.: the e¤ects of market interactions dominate the e¤ects of biological interactions. Consequences of the introduction of aquaculture conform to intuition: it is GOOD. Strong b.i.: the e¤ects of biological interactions dominate those of market interactions. The introduction of aquaculture may be BAD. In particular, when I < I < Iw (d1) introducing aquaculture may lead to a decrease in welfare, and even to the instability of the system and the collapse of both …sh stocks, which would have survived absent aquaculture. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 22 / 30
  23. 23. Improving the e¢ ciency of aquaculture Assumption: no biological interactions. Comparative statics exercise on k in the neighborhood of the interior steady state. An increase in k corresponds either to technical progress (technique e¤ect) or to a shift in the composition of the farmed product (composition e¤ect). Proposition (i) Long term stocks, e¤orts and prices in the edible …shery and the feed …shery evolve in opposite directions according to k. The evolution of catches depends on the initial state of the …sheries (heavily exploited or not). (ii) When the wild …sh stocks are heavily exploited in the initial steady state, the edible …sh stock and catch rise with k at the expense of the feed …sh stock and catch, while the e¤ort and the price decrease in the …rst sector and increase in the latest. The production of farmed …sh increases, and its price decreases. Consumer utility increases. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 23 / 30
  24. 24. Extension 1: Endogenous consumer tastes When consumer preferences depend on k (through α or σ), increasing k means not only having a more e¢ cient aquaculture technology (productivity e¤ect) but also breeding a composite product that consumers like less, or that is less substitutable to wild …sh (preference e¤ect). Proposition The e¤ects of an improvement in aquaculture e¢ ciency are completely reversed, if the weight a¤ected to farmed …sh or the elasticity of substitution between wild and farmed …sh becomes su¢ ciently low as the composite farmed product becomes less carnivorous. As k increases, the preference e¤ect may progressively dominate the productivity e¤ect. Our conjecture is that there exists a utility-maximizing farmed product composition. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 24 / 30
  25. 25. Extension 2: Regulation 1 We compare the reference case (wild edible …shery in open access, no aquaculture) to a situation where the wild edible …shery is optimally regulated. 2 We study the e¤ects of the introduction of aquaculture when: the edible …shery is regulated by a price-taker agency maximizing the present value of the in…nite stream of rents from this …shery; the feed …shery is either in open access or regulated by another agency; the two agency may either operate separately (they do not take into account biological interactions), or cooperatively (ecosystem management, optimum). E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 25 / 30
  26. 26. Wild edible …shery regulated, no aquaculture Proposition Absent aquaculture, at the interior steady state: (i) The stock of species 1 is higher when the wild edible …shery is regulated than when it is in open access. As a consequence, the stock of species 3 is lower. (ii) There exists a threshold level of consumer spending Ir (d1, r) < Iw (d1) under which the price of wild …sh is higher when the wild edible …shery is regulated than when it is in open access, and the catch lower, and above which it is the contrary. As a consequence, when I < Ir (d1, r), regulating the wild edible …shery makes consumers less well-o¤. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 26 / 30
  27. 27. Part (i): the purpose of regulation –the recovery of the …sh stock–is actually achieved, whatever the circumstances. Part (ii): regulation may not bene…t consumers, compared to open access. This is the consequence of the interaction of two e¤ects: 1 when the …shery is regulated, stock recovery =) increase of the catch =) decrease of the price; 2 the regulator has an incentive to increase the price and restrict the catch in order to increase the rent. When consumer spending is high, the …shery in open access is on the verge of collapsing. The …sh price spike is accompanied by a very low catch, which harms consumers. In this case, the …rst e¤ect of regulation dominates, and regulation is bene…cial to consumers. When consumer spending is low, the second e¤ect dominates, and regulation is harmful for consumers. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 27 / 30
  28. 28. Introducing aquaculture Proposition Absent biological interactions, from an initial situation where the capture …shery is optimally regulated: (i) the stock of species 1 (resp. species 3) is larger (resp. smaller) in the long run when aquaculture is introduced, and (ii) the pro…t of the edible …shery is smaller, whatever the management scheme adopted for the feed …shery. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 28 / 30
  29. 29. When biological interactions exist, introducing aquaculture leads to a decline in both the feed and the edible wild …sh stocks, and may lead to a decreased utility, in spite of the fact that more consumption options are o¤ered to consumers; except in the case of an ecosystem management of both …sheries. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 29 / 30
  30. 30. Conclusion Many hopes are placed in aquaculture. But we have shown that when biological interactions between the wild edible …sh population and the feed …sh population are strong, introducing aquaculture harms the wild edible …sh stock and may harm consumer utility as well. In the good case where the introduction of aquaculture is bene…cial, potential options in order to improve its sustainability: Improving FIFO ratios through technological progress (?). Finding a relevant substitute to feed …sh. Modifying consumer preferences (?) Further investigations needed to shed light on consumers’behavior towards farmed products. Anyway, from a food security point of view, aquaculture appears as a waste of animal protein since it removes quantities of …sh from the sea to produce lower quantities of …sh ‡esh. Feed …sh could directly be used as food. E. Regnier & K. Schubert (Paris 1 & PSE) Is Aquaculture Really an Option? A Theoretical Analysis VEAM 2015 30 / 30

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