Within minutes, the cloudbursts had entirely laid waste to the promise of a bountiful harvest carried by his plantation of organic olive groves, denuding each and every tree of its fruit.

"We basically lost the whole crop," Mercer said, with a tone approaching unsentimental resignation.

As it happens, the certified, award-winning organic farmer was, by that point, no stranger to extreme weather events, nor the increasingly erratic, punishing whims of shifting climate patterns.

A little over two decades ago, Mercer planted his dry range olive groves at Manna Hill Estate, situated along the foothills of Mount Egerton - some 30 kilometres east of Ballarat - blending the plantation with a mix of agroforestry using oak trees, chestnuts and hazelnuts as cover crops.

But his timing was quickly found wanting. The mass planting coincided with the prelude to the most brutal drought to have enveloped Australia since records began, spelling crippling conditions for farmers for years to come.

"The timing certainly could've been better," Mercer said. "The plantings survived but didn't really grow."

"At the time, the general consensus was that we should get a commercial harvest within three years of planting, but it took us 10 years."

What didn't survive the drought - the sheer severity of which science has since sheeted home to climate change - were several native trees endemic to the area, including some narrow-leaved peppermints, once viewed as among the hardiest of eucalyptus trees on earth. And, adding to the injury of the drought came the unheralded, ominous cry of the currawong, flocks of which - Mercer said - routinely strip his olive trees of their fruit, however ripe.

"As the climate's changing, the mix of trees and birdlife is changing," he told me, as we spoke under the canopy of some of his olive trees. Gesturing, he explained the avifauna of the area had altered markedly in recent years, pointing out he'd long since lost sight of a multitude of small, native birds that used to roam his farm.

"You know, people will often tell you to plant indigenous trees, but in actual fact you need to consider what the climate might look like in 30- or 50-years' time and plant trees that are going to survive.

"Similarly, when we first got here, we basically didn't have currawongs - this was the absolute extremity of their range historically - but now they're a long way south and we get large flocks of them, like 70 or 80 birds."

Currawongs, to Mercer's mind, were among those he considered the "winners of climate change", unlike human beings - including most people alive today - whom he ranked as among its greatest losers.

And it's an opinion grounded in scientific fact.

Much like the rapid rate at which extinctions and shifts in the historical range of birds have occurred, so too has the onward march of global warming repeatedly revealed the predictions of global-climate models to be overly optimistic. No longer is it accurate to view the consequences of climate change as a problem for future generations; the prelapsarian moment of our time, says Mercer, arrived years ago.

Notwithstanding those views, Mercer was at pains to point out he's no pessimist. On the contrary, he treats the existential gravity of climate change as a clarion call against the magnetic pull of both fatalism and denialism.

"There's an old Japanese proverb," he said, "which says, 'the best time to plant a tree is 20 years ago, the second-best time is now' - and that's absolutely right."

"You don't plant trees for your generation - my guiding principle, first and foremost, is about the impact [my actions] will have in the long term."

Mercer is a second-generation Victorian farmer, having grown up on a small, mixed farm in South Colac, surrounded by state forest. As a child, he walked and played among giants - vast, majestic trees, whose lifespans rendered those of individual human beings small and deceptively insignificant.

After finishing school in Ballarat, Mercer focused his mind on the particulars of engineering, maths and commerce, gaining qualifications in each field and seemingly committing to a career away from farming life. But in the 15 or so years that followed, his love for trees and the outdoors seemingly prevailed, returning him to the land.

Whether it was the looming and growing threat of climate catastrophe which prompted Mercer's change of scenery is unknown. What is known is that it was an unvarnished understanding of the great climate challenge that drew him to regenerative agriculture.

The practices of regenerative agriculture - a kind of farming that first emerged some 50 or 60 years ago - eschew the heavy dependencies of conventional and industrial agriculture on chemical fertilizers, pesticides and monocropping. Taking the health of soil as its centre point, regenerative agriculture promises to decarbonise farming and reduce global warming by employing techniques - such as cover crops, shelterbelts, agroforestry and crop rotation - that aim to improve, rather than degrade, the biodiversity of the soil.

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Importantly, Mercer explained, regenerative agriculture was not to be conflated with its poor cousin, sustainable agriculture - a form of farming which, though an improvement on conventional agriculture, doesn't promise to restore the ecosystem and is therefore not bold enough for the challenge of our times.

"We're past sustainable agriculture, which is essentially about not making things any worse," Mercer said. "Clearly, given where agriculture is today, even if things didn't get worse, that would be a bad place to be," he added.

"Regenerative agriculture is about restoring soil biodiversity, so that [the soil is] more resilient and can hold more carbon - the more carbon it holds, the more water it can hold and so is more resilient to things like drought and intense rain."

Across Europe and in countries like the United States, the peregrination of regenerative agriculture from the margins to the mainstream runs in tandem with the dawning urgency of the need to address climate change.

But in Australia, it continues to lack a mainstream footing, despite its proven enviro-economic return. To explain this, Mercer - drawing on his commerce background - zeroed in on basic human psychology.

"It's about incentives," he said. "Corporate farming is all about [the maximisation of] short-term profit and currently all the incentives in the industry go the opposite way [to regenerative agriculture]; farmers are actually disincentivised from doing a lot of the things associated with regenerative agriculture."

"So, we need to remove the incentives to stick with industrial agriculture - including the way fossil fuels have been subsidised - and put incentives in place that would actually encourage them to go down the path of regenerative agriculture."

In other words, what Mercer argues for is the implementation of economic incentives that enables farmers to lead the way, such as - for example - paying farmers to keep carbon in the ground.

Standing in the way of that shift in approach, however, was - in Mercer's opinion - the difficulty posed by the consolidated landscape of farming across Australia - a product of the "get big or get out" neoliberal mantra of the 1980s.

"Whether you think it was a good thing or a bad thing, it drove a lot consolidation, so that as a political bloc, farmers are minute these days," he said, adding that the National Party no longer represented the "average farmer or rural community at all".

Viewing the circumstances as a whole, Mercer therefore doubted regenerative agriculture would ever verge on the mainstream, much less become mainstream, in Australia without a society-wide push for a profound shift in priorities.

But he didn't suggest such a shift was impossible, stressing this was neither the place nor the time to give in to fatalism.

"As an individual consumer, people have no power: agreed. But collectively, they've got unbelievable power and should never underestimate it," Mercer said.

Seemingly small, individual acts, like strengthening small supply chains by buying from local independent grocers, farmers' markets or even direct from the producer, or investing in renewables, recycling and voting wisely, can, in Mercer's view, create the demand and impetus required to force the hand of government.

"For government to say, 'well, we're not going to do anything about climate change' is just morally reprehensible - it's just tunnel vision," he said.

"We know the window to addressing climate change is closing at tremendous speed - some have even predicted societal collapse by 2040 - and so it's easy to feel there's nothing you can do about it.

"But, as [anthropologist] Margaret Mead said, 'you've got to be the change that you want to see in the world'."

The onus, in Mercer's view, is on all of us to rise to the occasion by discarding our posture of powerlessness and reckoning not just with the fact of ecological devastation, but the varied ways our individual actions contribute to climate change.

The inevitable alternative, of course, is a forced reckoning with the irrevocable tipping points of global warming, which - science tells us - promise to fell humanity as easily as the drought did those ancient eucalyptus trees on Mercer's farm ten years ago.

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