Between 1904 and 1916, whaling stations in South Georgia — a remote British island in the South Atlantic — processed approximately 175,000 whales. Humpbacks were among the first targeted: slow enough to catch, rich enough in oil to make the voyage worthwhile. In a single decade, the South Atlantic humpback population was reduced from an estimated 27,000 animals to fewer than 450. A species that had sung across the southern ocean for millions of years was functionally silenced.
Today, that silence is over.
A landmark population assessment published in 2024 in *Royal Society Open Science* — and widely cited in 2025 and 2026 as the definitive accounting of the recovery — found that South Atlantic humpback whales (*Megaptera novaeangliae*) have returned to approximately **93% of their estimated pre-whaling population levels**. Based on modelling of pre-exploitation abundance and current census data from the International Whaling Commission and partner institutions, the study places the current South Atlantic population at around **25,000 individuals**, compared to a pre-whaling estimate of approximately 27,000.
For a species that was *functionally extirpated* in one of the most heavily exploited ocean regions on Earth, that number represents something close to a miracle.
**How We Almost Lost Them**
Humpback whales are not built for speed. They filter-feed on krill and small fish, they migrate predictably along coastlines, and they breed in shallow, warm waters where ships can easily follow them. In the age of steam-powered catcher boats and explosive harpoons, those characteristics made them ideal targets.
The scale of the slaughter is difficult to comprehend. In the South Atlantic and Southern Ocean combined, an estimated **200,000 humpback whales** were killed during the commercial whaling era, primarily between 1904 and 1963. The International Whaling Commission, established in 1946, initially did little to stop the killing — quotas were set based on what the industry wanted, not what the biology could sustain.
By the early 1960s, populations had collapsed so severely that commercial whaling became unprofitable on its own terms. The whales were simply gone.
**The Laws That Saved Them**
Three international agreements form the backbone of the humpback's recovery:
- **1963:** The IWC imposed a moratorium on all Southern Hemisphere humpback whaling — the first major whale protection measure. - **1973:** The US Endangered Species Act listed humpback whales as endangered, triggering protections for American waters. - **1986:** The IWC implemented a global commercial whaling moratorium across all species and all oceans — a moratorium that, despite ongoing challenges from Japan and Norway, has held for nearly 40 years.
And then, slowly, the whales came back.
**The Recovery in Numbers**
The return of South Atlantic humpbacks has not been uniform — it has unfolded across decades, one animal at a time:
- 1970s: Surveys estimate fewer than 1,500 survivors in the South Atlantic - 1990s: Photo-ID catalogues begin documenting individual whales; population showing signs of growth - 2010: An estimated 10,000–15,000 humpbacks in the South Atlantic breeding grounds - 2020: Population modelling suggests 20,000+ individuals - 2024: Comprehensive assessment: **~25,000 individuals — approximately 93% of pre-whaling levels**
Growth rates in certain breeding populations — particularly the **Abrolhos Banks breeding ground off Brazil**, which hosts the largest concentration of humpbacks in the South Atlantic — have been documented at 7–12% per year in recent decades, among the fastest recovery rates of any large whale species anywhere in the world.
**What 93% Means**
A 93% recovery does not mean the work is done. The South Atlantic ocean ecosystem has changed fundamentally since pre-whaling days: krill populations are declining due to climate change and ocean acidification; shipping traffic has increased dramatically; noise pollution complicates the long-distance communication humpbacks depend on; and entanglement in fishing gear remains a significant cause of mortality.
But ecologically, the humpback's return matters in ways that go beyond the emotional. Humpback whales are what ecologists call **ecosystem engineers**. Their feeding dives mix nutrient-rich deep water to the surface, fertilising the phytoplankton blooms that form the base of marine food chains. Their faeces — rich in iron and nitrogen — directly stimulate krill and fish production. A healthy whale population makes the ocean more productive for every species in it, including the fish stocks that feed hundreds of millions of people.
The recovery of 25,000 humpback whales to the South Atlantic is not just a conservation milestone. It is the partial restoration of a biological process that industrial whaling interrupted — and proof that, given time and protection, the ocean can still heal itself.
**The Oldest Living Memory**
One remarkable aspect of the humpback recovery is that some of the survivors still alive today were born before commercial whaling completely collapsed the population. Humpback whales can live 80–90 years. There are animals in the South Atlantic whose earliest memories — to the extent that whales have memories — include ocean soundscapes that humans have never heard: the songs of a full, abundant population, before the ships came.
Those animals, and their calves, and their calves' calves, are swimming in those waters again.
93% of the way home. 🐋
*Sources: Royal Society Open Science — South Atlantic Humpback Population Assessment (2024) · International Whaling Commission · IUCN Red List · NOAA Fisheries · Ocean Alliance · Instituto Baleia Jubarte (Brazil) · WWF Global*
