Extreme weather events, including one of the hottest years on record, had a huge impact on wildlife here in 2020.
And there was a warning that man-made problems such as increased littering and more wildfires were also having a detrimental effect.
However, many species have seen a boost due to the pandemic lockdown, the National Trust said. Fewer people about during the peak breeding season of spring saw wildlife thrive in locations normally considered tourist hotspots.
Herons were seen on the lake at Mount Stewart and badger cubs spotted playing in the grounds during daylight.
And at the Giant's Causeway, reduced footfall on the stones allowed the Sea Thrift - or 'Sea Pink' flower - to flourish among the basalt columns, a sight that is rarely seen.
More evidence of this came with the news that just two years after barn owl nesting boxes were introduced to Mount Stewart the estate was celebrating the arrival of a breeding pair and the hatching of four chicks.
Lead ranger Toby Edwards said: "It's thought that there are less than 30 pairs of barn owls in Northern Ireland, with the species having been in decline here for some time."
Globally, 2020 is likely to be one of the three warmest years on record, creating the perfect conditions for some species to thrive, particularly certain birds, butterflies and moths.
In August the National Trust announced the first recording of the False Cacao moth at Murlough nature reserve. The discovery brings the species count for moths and butterflies at the reserve to 793, the largest recorded at a wildlife site here.
But despite new recordings, 2020 was a worrying year overall.
"Unfortunately, summer was not blessed with an abundance of butterflies and this data comes shortly after the publication of two key reports in 2019 which showed that nature is in crisis," said Melina Quinn of the National Trust.
Its Strangford Lough rangers reported the final grey seal pup count this year was 187, six more than last year and another record.
The Brent geese count was 26,475 birds compared to 20,965 in 2019.
The warm summer and Covid travel restrictions provided an opportunity for more people to explore the nature on their own doorstep - but with an unfortunate outcome.
Trust rangers reported that big increases in fly-camping and people littering at beauty spots such as the Mournes, Murlough and parts of the Causeway Coast, meant they were spending more time clearing up the mess than protecting nature.
Sean Maxwell, climate and environment adviser at the National Trust, said: "Climate change is already having an impact on our wildlife.
"We, like the wildlife that calls these places home, must learn to adapt, but importantly we must find solutions to preventing the worst that climate change has to offer."