Clean Air and Climate Change: London's Increasing Bryophyte ...

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

Middlesex 34 species (8 liverworts and 26

mosses) have been added since 2000

Hampstead Heath 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), Scratchwood, Ruislip 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 oak

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 oaks. 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