EVERYBODY is missing the complexity, the indications of the essential path forward, and how much this has irrevocably stunted life on Earth - even Joe Roman, the cited leading authority on whale ecology.
First, there are two type of whales, baleen and toothed. Baleen whales are surface photozone filter feeders living on massive amounts of plankton and small fish. Toothed whales are bottom hunting carnivores who live on large pray like kraken and other cuttlefish. The former depend on the latter, as do the photosynthetic plankton that are the base of all oceanic life, which historically supplied 70% of the world's Oxygen and provided 70% of the global CO2 mitigation.
HOWEVER, according to Boyce and Worm, we have lost 70% of the global phytoplankton sometime in the last 120 years, and this factor has not been included in any climate models or soil fertility studies. The endangerment of whale populations are related, because Roman showed that each toothed whale brings up 3 to 5 tons per day of organic material from a kilometer down. This includes all the bio-essential mineral elements that feed the plankton, and thence all other oceanic life. The human hunting of whales is therefore the most likely leading cause of the 70% drop in life on the surface. Without the "whale pump", we will remain in a vicious circle.
The drop in nutrients in the ocean is reflected in a lack of restoration in terrestrial soil elements. Every year millions of tons of nutrients flow in rivers and groundwater to the sea. Nature's balance required that those elements be balanced by upstream movement from salmon, herring and eels that grow in the ocean and then return upstream to spawn. These have been overfished and blocked by dams and excessive water use for meat production, crop irrigation, landscaping, flush toilets, etc. Now they are getting farmed, which is an environmental disaster!
Water borne sanitation and unsustainable chemical fertilizer have accelerated the depletion of soils to feed humans and their livestock, and further poisoned the rivers and estuaries for aquatic life, in addition to runoff from all drilling and mining operations.
Motorized shipping, underwater mineral exploration and exploitation, high powered sonars and now wind farms generate noise pollution that confuses, injures and kills cetaceans that rely on sound for all their activities - hunting, feeding, mating and raising their young.
SO, restoring the whale population will take a long time because the lack of whales is a limit to the growth in their population. What we need to undo our grievous injury to the ecosystem is halt all motorized shipping, all drilling and mining, shut down wind farms, halt chemical fertilizer, stop irrigation, flush toilets and food markets, and return to 100% bio-compatible, 100% recycled economy.
Further, 90% of the excess anthropogenic heat has gone into the ocean and is now melting permafrost on the sea bed and releasing massive amounts of diffuse Methane emissions. This is getting eaten by methanogenic organisms in the benthic zone, deplating the oxygen in the deeps and converting to CO2. When the Oxygen in the lower layers is used up, there will be a massive surge in Methane emissions from the ocean and it will be game over for Oxygen breathers.
There will also be a total die-off of Oxygen breathing life forms on the bottom, which will eliminate the food supply for bottom feeding whales and stop the cycle totally in a final whale die-off.