Sustainable resource management

Distinguish between renewable and non-renewable resources by applying them to these three cases: a fishing ground, a riparian forest, and a coal deposit. Explain what condition must be met for a living resource to continue behaving as renewable.

Define natural resource and classify these four as renewable, renewable only if well managed, or non-renewable, justifying your answer: water from a fossil aquifer, timber from a managed forest, oil and wind.

Define overexploitation and give a real example of an overexploited living resource, explaining what signal indicates that exploitation exceeds the resource's capacity for renewal.

Explain what the renewal capacity of a living resource is and what happens when the extraction rate exceeds it continuously, giving a fishing or forestry example.

The graph represents the natural renewal rate of a fishery according to its population size and the fleet's annual catch. a) Interpret why renewal is zero at both extremes and maximum at intermediate sizes. b) Explain what point '?' represents and what will happen to the population if the catch remains higher than the renewal rate.

A fishing ground is estimated to have a stock of $100\,000\ \text{t}$ of a species, with a natural renewal rate of $8\ \%$ per year. a) Calculate the theoretical maximum sustainable catch. b) Explain what will happen to the stock in the following years if the fleet catches $10\,000\ \text{t}$ per year. c) Indicate two uncertainties of the model that could make that figure unsafe.

A fisheries management model based on Maximum Sustainable Yield (MSY) estimated the carrying capacity (K) of a hake population at 100,000 t and set a constant annual quota at the theoretical value of maximum productivity, assuming that the stock should stabilize at K/2 (50,000 t). However, after four years of rigidly applying that quota, the spawning stock biomass collapsed to less than 15,000 t.

1. a) Justify, using the logistic population growth curve, why managing a population by permanently keeping it at K/2 constitutes an unstable equilibrium point in the face of unforeseen environmental fluctuations (such as thermal anomalies or drops in recruitment).
2. b) The classic MSY model treated the population as a homogeneous mass of biomass in kilograms. Explain what crucial biological factors (such as age structure, the exponential fecundity of large spawners, and gear selectivity) this calculation ignored and how this precipitated the collapse.
3. c) Design a harvest control rule under the precautionary approach for this fishing ground: define a limit reference point (Blim) and a precautionary or target reference point (Bpa), and detail what automatic quota adjustment or moratorium measures must be triggered if the stock drops into each of these zones.

Explain what these three tools of sustainable fishing consist of — closed seasons, catch quotas, and minimum size limits — and what biological objective each pursues.

Explain what information a fisheries manager needs to set a responsible catch quota (stock size, age at first reproduction, annual recruitment) and what risk the fishery runs if the quota is set using outdated data.

Deforestation of a forest triggers a chain of effects on climate, soil, and biodiversity. Explain this chain of effects and relate it to the increase in atmospheric $\text{CO}_2$ and the loss of ecosystem services.

Compare a short-rotation eucalyptus plantation intended for paper pulp with a native mixed forest of the same county: timber productivity, hosted biodiversity, fire risk, and ecosystem services. Conclude which criteria should guide new plantations.

Explain what the "tragedy of the commons" is using an open-access fishing ground, and analyze how three tools try to avoid it: individual quotas, fishing reserves managed by fishermen's associations, and marine reserves.

An anchovy fishery is depleted after decades of overfishing. Design a management plan to recover it: closed-season measures, scientific monitoring of stock, enforcement control, and a reopening schedule, justifying each decision using the species' biology.

A large industrial purse seine tuna company operating in the Indian Ocean has obtained a prestigious blue certification for sustainable fishing to market its canned products in the European Union. However, an independent audit reveals three facts: 1) the fleet uses fish aggregating devices (FADs) that result in 15% accidental bycatch of sea turtles and juvenile sharks; 2) local artisanal cooperatives catch tuna one by one with handlines with virtually no discards, but lack certification because the initial audit costs over 35,000 dollars; and 3) independent observers are only present on 10% of the certified fleet's fishing trips.

1. a) Critically evaluate whether this certification guarantees genuinely ecological exploitation or whether it is a case of greenwashing, justifying your answer with the selectivity and monitoring data.
2. b) Analyze how this voluntary labeling system distorts market competition, penalizing artisanal fisheries with lower environmental impact compared to large industrial fleets.
3. c) Based on this case, refute the argument that "global overfishing can be stopped by relying on individual responsible consumer purchases" and propose two binding public regulation measures that governments should officially impose on all fleets.

Describe two practices that distinguish organic farming from conventional farming (use of inputs, soil management, pest control) and explain what the USDA Organic label guarantees.

Aquaculture already provides nearly half of the fish consumed worldwide. Analyze two advantages and two environmental impacts of fish farms, and explain whether they can be considered the definitive solution to overfishing.

The Aral Sea went from being the fourth largest lake in the world to almost disappearing when the rivers that fed it were diverted to irrigate cotton. Reconstruct the chain of decisions and of local ecological, social and climatic effects, and draw a lesson applicable to the management of American rivers such as the Colorado River.

Distinguish between water stress and drought, and compare two water management philosophies: increasing supply (inter-basin transfers, desalination plants) versus managing demand (irrigation efficiency, reuse, water rates). Indicate one advantage and one limit of each philosophy.

Two adjacent 10 ha agricultural plots in the same region show the following annual balances: Plot A (intensive) produces 45 t/ha of citrus fruit, applies 200 kg N/ha in synthetic inorganic fertilizers, uses flood irrigation, and consumes 14,000 kWh/year in machinery and pumping; Plot B (organic) produces 28 t/ha with cover crops, applies mature compost at a rate of 80 kg N/ha of organic nitrogen, uses drip irrigation, and consumes 6,500 kWh/year.

1. a) Predict and justify what quantitative and qualitative differences will be observed between both plots regarding nitrate leaching into groundwater, nitrous oxide (N₂O) emissions into the atmosphere, and the rate of soil carbon sequestration.
2. b) A technical report claims that "given that Plot B produces fewer kilograms per hectare, its ecological footprint per ton harvested is necessarily worse for the planet than that of Plot A". Refute this statement by analyzing the fossil energy embedded in the synthesis of inorganic fertilizers (Haber-Bosch process) and the long-term degradation of natural capital.
3. c) Identify two negative environmental externalities of Plot A that are not reflected in the final market price of its citrus fruit, and propose a policy or economic measure to internalize the real costs.

In an Extremaduran dehesa, livestock farming, hunting, and the conservation of threatened birds coexist. Outline the potential conflict between economics and conservation and propose a management model that makes them compatible, explaining which ecosystem services the dehesa supports.

A district lives off intensive irrigation that is depleting its aquifer. a) Analyze the conflict between current employment and the sustainability of the resource. b) Design an orderly transition (changing crops, modernizing irrigation, reuse, water pricing) that reduces extraction without abandoning the district. c) Discuss who should pay the cost of the transition and why.

Compare three sources of protein for the American diet — capture fisheries, aquaculture, and pulses — in terms of trophic efficiency, ecological footprint, dependence on external resources (feed, fishing grounds), and impacts. Argue which combination would be most sustainable and what changes in consumption it would imply.

During a sunny and windy midday in April on the Iberian Peninsula, instantaneous wind and solar photovoltaic generation reaches 105% of electricity demand, causing the wholesale market price to plummet to 0.0 dollars/MWh and forcing the system operator (REE) to order renewable curtailment (disconnection of farms). However, at 22:00 on that same day, natural gas combined cycle power plants have to provide 30% of the electricity consumed.

1. a) Based on these data, interpret the difference between installed capacity and grid dispatchability, and justify why indefinitely increasing the number of solar farms does not solve nighttime demand on its own.
2. b) Evaluate two viable technical solutions to store or manage this daytime surplus in Spain (such as pumped-storage hydroelectric power plants and green hydrogen), comparing their net energy efficiency and their potential land-use or environmental encumbrances.
3. c) Refute the claim that "the energy transition simply consists of replacing fossil fuel generators with renewables to maintain the current pace of consumption", arguing why energy saving and efficiency policies are essential in the face of the biophysical limits of critical materials and land.