Clean Air and Climate Change: London’s Increasing Bryophyte Biodiversity

Silvia Pressel and Jeffrey G Duckett Researchers in Biodiversity Life Sciences Natural History Museum Today’s presentation

1. An overview of London’s mosses and liverworts focussing on London and in particular the effects of the Clean Air Acts (1956, 1968).

Acknowledgements. Our thanks to generations of British bryologists who collect distribution data. Hunter Gatherers: Some of the 700 members of the British Bryological Society BRYOPHYTES

• Mosses, liverworts and hornworts

• Most primitive of all land plants –present day bryophytes had ancestors going back to 470-480 MYA when plants first colonized land.

Some numbers

• Bryophytes are very important components of terrestrial ecosystems. • 6% of the world’s carbon is locked up in the bog moss Sphagnum, living and dead. We destroy this at our peril.

The World • Mosses 10-12,000 species • Liverworts 4-6,000 leafy, 350 thalloid • Hornworts 200-250 • Flowering plants 450,000 • Ferns 10,000

Sphagnum-the bog moss Kenwood Bog The commonest liverworts in London • Marchantia polymorpha • Lunularia cruciata

In pavement cracks, greenhouse pots

London numbers

Middlesex c 200 Includes canals and rivers, chalk and heathlands in the north west 34 species (8 liverworts and 26 mosses) have been added since 2000 146 (91 in 1998) Why are bryophytes so small? 1mm -1m cf flowering plants 1mm-100m Why don’t we see tree mosses and liverworts? • Need to think about the problems of living on land. • Intermittent and uneven water supply • Alternative strategies to deal with this; • Homiohydry –maintaining water balance • Poikilohydry – drying out and rehydration- desiccation tolerance. The bryophyte and lichen strategy Homiohydry permits the growth of large plants, poikilohydry imposes severe limits on growth When the plants are desiccated they are quiescent –this does however allow them to grow in some pretty inhospitable places eg bare rocks and deserts. Within minutes of rehydration they begin to grow again -1 shower/year . Some are extremely slow growing <1mm/year and are almost certainly very very old –probably older than the oldest trees Extreme desiccation Syntrichia desertorum London LONDON

• London (Middlesex and North Surrey) is a very urban environment • Humans destroyed natural habitats a long time ago Oliver Rackham –of the 12 earliest known herbarium plants from Hampstead Heath (16 century), 6 no longer grow there eg Drosera (sundew) –must have been a wonderful valley bog full of Sphagnum all destroyed when the ponds were constructed. • The only near ‘natural’ vegetation is to be found on parts of Hampstead Heath (Kenwood is ancient woodland), , Woods, Queen’s Wood. Sphagnum –on the site of the ponds

The Industrial Revolution

• Urbanization was only one factor that destroyed bryophytes with it came air pollution - soot and sulphur dioxide. • Why are lichens and bryophytes so sensitive to air pollution? • Adapted to absorbing nutrients in very low levels • The future NOX? London’s Woods in 1970

• Ancient Woodland – Oliver Rackham • Managed as standards and hornbeam coppice • Woodland floor with indicator species Oak standards and hornbeam coppice Before the Clean Air Acts

• London was a mucky place • Sulphur dioxide and soot in 1970 • Blackspots >200ppm • London , Birmingham. The North of England 1970

• Moths on soot-blackened trunks • Melanism –dark coloured varieties • Several moth species >50% melanic Peppered moth Biston betularia var typica and var. carbonaria Woods in 1970

• Epiphytes Lichens and bryophytes • Wholesale extinctions since the industrial revolution – why? • Depend on rain for nutrients, killed by flooding with sulphuric acid • Hampstead Heath only 5 epiphytes cf >25 today Woods in 1970

• Tree trunks Bare wood often >50%, alga (Pleurococcus) and one lichen Lecanora conizaeoides

• Tree bases bryophytes confined to bottom 20cm and only 3 species Bare bark Bare bark –one lichen one green alga Pleurococcus and Lecanora Today after the Clean Air Acts of 1956 & 1968

• Epiphyte recolonization to the extend that London’s woodland trees are not very different from those in the deepest countryside of S E England

• Much less bare wood

• Very little Pleurococcus

• Lecanora conizaeoides Almost extinct-competition

• Mosses and liverworts all the way up the trunks and onto the branches - up to 25 species

Epiphytes on . A major change in the last 20-30 years

• Today mosses growing up the trunks

• Lecanora conizaeoides virtually extinct Orthotrichum pulchellum, Cryphaea heteromalla and lichens

Why have London’s bryophytes increased in number?

Better bryologists?

Clean air - much lower sulphur dioxide and soot but more oxides of nitrogen

Climate change

Orthotrichum lyellii Cleaner air Ted Wallace 50 years ago wrote ‘a declining species in Surrey’

1981 Frullania dilatata Cleaner air Ruislip Woods 1969

Cryphaea heteromalla Cleaner air + Climate Change Ulota phyllantha

Ulota phyllantha Climate change - previously western and coastal Cololejeunea minutissima Climate change - perhaps the most dramatic example The Future

• We have a ‘hit list’ and many of the plants on it will undoubtedly turn up. But in addition there will be surprises • Current projects (NHM) The City The Highgate Cemeteries The Thames and other waterways Hampstead Heath Conclusions

• London bryophytes are extremely beautiful • There is a lot of bryophyte diversity in London • The flora has changed radically in the last 30 years • The flora is still changing • Bryophytes can give wonderful insights into air quality and climate change • ‘If a bryologist is tired of London he/she is tired of life’ Threats: mainly habitat losses

• Cutting down specific trees • Ash dieback, as this tree supports diverse epiphytes • Cleaning of stonework Leave stonework alone!!

Gymnostomum viridulum Mediterrannean species Winchester Cathedral and Highgate Cemetery Bryophyte Projects

• Recording –requires specialist knowledge • Reproductive cycles • Epiphyte distributions- new trees, spread on existing trees • Recording pollution

Reproductive cycles

• Easy to record • All new data • 4 very common London mosses Grimmia pulvinata Bryum capillare Bryum radiculosum Tortula muralis Grimmia pulvinata Tortula muralis Jan to July Bryum capillare Jan to Aug Bryum capillare 2014-15 very successful reproduction but---- Roadside trees –major recolonization since 2000 Tufnell Park 2005 and 2012 Frullania dilatata Ruislip Woods 1969. Mile End 2008. Tufnell Park 2014 The British Bryological Society http://www.britishbryologicalsociety.org.uk/

• Field Guide on line • Excursions –local and to all parts of the British Isles • Free tuition and new discoveries almost statutory