Urgent action is needed to curb the “enormous volume of pesticides” used in UK farming which is damaging wildlife, Chris Packham has urged.
The TV presenter and naturalist also called for more incentives for farmers so they can help reverse declines in nature in the countryside.
Farmland birds, butterflies and bees have all suffered significant declines in numbers, while wildflower meadows have largely vanished.
Mr Packham has launched a 10-day “bioblitz” campaign, joining experts to assess the wildlife found in 50 locations in the UK.
He said farmers were good at turning around declines in the countryside but not enough land managers were carrying out conservation efforts across a broad enough area.
He said: “We need more incentives for them to do that. That means subsidies, it means making sure the schemes we offer them are practical and work, making sure they can actually implement them..
“We need to make sure our farmers are properly rewarded for their endeavour and not running overdrafts because they haven’t got their grant yet.” He also warned of the effect on wildlife from practices including the use of pesticides.
“It’s clear the enormous volume of pesticides that we throw at the UK landscape is having a detrimental effect on many things, notably insect populations,” Mr Packham said.
He said insects were being hit by the “extraordinary tonnage of these poisons that we’re throwing on the landscape”, with knock-on impacts for species that feed on them.
There was a need to get rid of toxic substances, he said, pointing to neonicotinoids, now largely banned over links to bee declines.
Questions needed to be asked about the “enormous volume” of glyphosate used on the countryside, though he said the weedkiller was useful as part of “no-till” farming which can protect soil quality.
But he said: “Ultimately we need to be working towards a more organic system of farming.
He said farmers were already managing the land more for wildlife “without too much in proper incentives”.
And there was an opportunity to provide better incentives which could lead to a far greater uptake by farmers post-Brexit.
On Sunday Mr Packham is visiting Papley Grove Farm in Cambridgeshire, where farmer Martin Lines, chairman of the Nature Friendly Farming Network, has tailored his farming methods to support wildlife.
Mr Lines said that by carefully changing his methods he could increase wildlife, such as barn owls, and run a successful business.
He said: “I feel lucky when I see our wildflower areas and hedgerows attract lots of bees and new butterfly species. I love the fact that rare species such as skylarks and corn buntings soar overhead singing while I work on the land.”
But he warned: “Our efforts are irrelevant if other farmers do not recognise a shift to nature-friendly farming is not just good for wildlife but is key to the long-term survival and success of British farming.
“By working together, we can enhance and improve our countryside for all to benefit, but we need the right government policies and public support in place to help us fulfil the potential farmland has for conservation.”