Much of modern conservation works to baselines of species diversity and abundance set in modern times of the last 50-70 years. The recent forgotten fish report outlines freshwater fish declines since the 1970s, of 76% declines in migratory freshwater fish populations and 94% declines in populations of freshwater mega-fishes (fish heavier than 30kg). Despite these shocking numbers, the report highlights a key issue in modern conservation, that our parameters for success must be based on coherent ecosystems and not degraded ecosystems. Because reliable data only became available in recent history our baselines to report against are set against that data. The problem with baselines set in this timeframe, particularly in the UK, is that high intensity exploitation of our natural world has been going on for hundreds, if not thousands of years before the 20^th century. This means that we had already forgotten much of the wildlife/fish we have lost before we started measuring it. Setting the baselines based on what the environment looked like in the 20th century is an example of the well known Shifting Baseline Syndrome where recent experience becomes established as the new normal. By setting the baseline in recent times, in the absence of large megafauna such as whales, in the absence of ecosystem engineers like beavers, wild boar and wolves, and in the absence of the historical abundance of common species such as migratory fish, we establish that baseline as normal. And that means that our sense of achievement at reaching or conserving those baselines is misplaced.

The impact this can have on perception of success in conserving and restoring our natural world is stark. If we compare current ideas of success here in Western Europe against the qualitative evidence of historical sources for what the natural world was like we can see profound differences.

Freshwater and Marine Ecosystems

Despite setting the fisheries baselines in the 1970s the UK has some catch data going back to 1889. After correcting for fishing power (amount of time and effort spent fishing vs size of nets and sail/engine power available) some studies estimate we have lost 95% of bottom living fish from our marine waters (for some species as high as 98%) since 1889. Using cod as an example, in the NW Atlantic cod biomass has collapsed by approximately 96% since 1850 and fish have also shrunk. Historically NW Atlantic cod at 3 years old averaged 3kg in weight, now they average 1.3kg at 3 years old. Enormous areas of the shallow continental seas of the English Channel, North Sea and Irish Sea were covered in native oyster beds, with the Firth of Forth oyster bed covering 100 square km and producing 30 million oysters a year. They were almost entirely wiped out by trawling, pollution and disease by the early 1900s and have not recovered today. We see accounts of one day’s fishing on 2 miles of river in North America in the 1700s resulting in capture of 600 Sturgeon (fish up to 5.5m long and 600kg in weight). This kind of abundance of large fish is unheard of in modern times in Europe or the USA but there is no reason to suspect that European habitats didn’t once support similar populations of species such as sturgeon, and no reason European habitats couldn’t support similar abundances once again if they were fully restored.

Terrestrial ecosystems

In our terrestrial ecosystems here in the UK we set the baseline in the complete absence, or with tiny numbers of species such as beavers, wild boar, lynx, wolves, white tailed eagles etc. These species fulfil roles in their ecosystems, and most of them have no other native functional alternatives. Nothing else in UK ecosystems does what a beaver does for example. It is hard to imagine a UK today with healthy populations of all these species, and to envisage all the ecosystem effects that these species had. How many of our rare or declining species today relied on ecosystem effects resulting from the presence and interaction of one or many of these species? The book Rebirding recounts one estate in Scotland killed 27 white tailed eagles, 15 golden eagles, 18 ospreys, 275 red kites, 63 Goshawks, 462 Kestrels, 285 Buzzards, 63 Hen Harriers and 198 wildcats between 1837 and 1840. Just three years. Now imagine those population levels in all appropriate habitat across the UK. What must the abundance of prey been like to support such numbers of predators? That is a very different looking UK, and in very recent times ecologically speaking. If we add on the losses since the mid 20^th century – 97% declines in tree sparrows since 1970, 93% of grey partridge since 1973 then we can see that we are left with the bare vestiges of once healthy ecosystems.

Imagine as a thought experiment if we took out all the elephants, rhinos, giraffes, water buffalo, zebra, lions, african hunting dogs and so on from African ecosystems, let the ecosystem run for a few decades and then set a baseline. This is effectively what we have done in setting baselines for our ecosystems in the UK and Western Europe. Ecologically it’s madness. It’s the equivalent of stripping an engine of half it’s parts and then setting that as an example of a good engine and trying to keep it going in that state.

Rewilding in essence is a movement and a philosophy to challenge shifting baseline syndrome and reconsider what a successful and fully functioning ecosystem with healthy populations of species looks like. We need to take the philosophy of rewilding and apply it in mainstream conservation. Taking this approach would change our ambition by changing the conversation. A 20% increase in a species population sounds great, but if that 20% increase is on the remaining 5% (in real terms a 1% increase against historical/potential levels) then that changes our idea of success and what our ambition for success is. Imagine applying this thinking to modern fisheries quotas, where we are likely mostly fishing the last 5% of potential biomass? Measuring our success against estimates of what we think systems could support in a fully restored state is a far more ecologically sound approach to tackling the nature crisis and gives us an idea of how much potential we are missing out on. Imagine the difference in the amount of effort needed for fish caught in a degraded versus fully restored ecosystem? Or how much carbon might be sequestered by fully restored and functioning ecosystems? We’re missing out on huge amounts of productivity that are likely almost unimaginable for most modern people.

We don’t have the exact data to say what exactly restored ecosystems would be like in the UK or in Western Europe, but we can’t let that hold us back. The truth is that the historical qualitative and genetic evidence is so overwhelming in its depiction of a world of abundant ecosystems that it is irrational to discount that as usable data. We can take historical and qualitative evidence and combine that with modern ecological knowledge to develop estimates of what fully functioning modern ecosystems should look like. We need to be comfortable with estimates and be more nature led, restoring what we think is a functioning ecosystem and seeing where it gets to.

Things are going the right way, opinions and ambitions are changing. Now it is time for our governments, statutory bodies and leading conservation organisations to take on and apply this latest ecological thinking and understanding. We need to reassess what we consider normal, face how far we have to go and up our collective ambition. This will require a change of mindset, from proving why to proving why not. Why isn’t this species native, why not reintroduce this native species, why shouldn’t we completely restore this habitat? This would be a nature led approach to ecosystem restoration, where we put the pieces of the engine back together and see how far it takes us.