How much habitat is enough?

Question 1

IPBES report messages 2018

Answer 1

Land degradation occurs in all parts of the terrestrial world. Combating it and restoring degraded land is an urgent priority to protect the biodiversity and ecosystem services vital to all life on Earth and to ensure human wellbeing.
Without urgent and concerted action, land degradation will worsen in the face of human population growth, unprecedented consumption, and climate change
The implementation of proven actions to combat land degradation will become more difficult and costly over time. An urgent step-change in effort is needed to prevent irreversible land degradation and accelerate restoration

Question 2

IPBES key observations

Answer 2

Less than one quarter of the Earth’s land surface remains free from substantial human impacts
Habitat loss and degradation of the remainder are the leading causes of biodiversity loss. Other important causes are climate change, over-exploitation, invasive species and diseases, and pollution.
Alienation of indigenous peoples from the land often leads to irreversible loss of knowledge on land management. Indigenous land management is generally sustainable over long periods, unlike current practice.
Even the most optimistic scenario tested projected mean loss of species abundances in excess of 35% globally by 2050.
There is an overwhelming economic case for habitat restoration (globally, the benefits of restoration are ~10 times the costs) and yet there is still not much done.
Information systems are needed to monitor progress and improve outcomes.

Question 3

Radford et al (2005)

Answer 3

24 x 10x10Km landscapes of 2% to 60% tree cover - dispersed or aggregated to see impact of fragmentation
Most species negatively affected by habitat loss
Below 10% tree cover = community collapse
Need at least 35%

Question 4

population connectivity

Answer 4

the combination of demographic connectivity and genetic connectivity
important for persistence of populations by recolonisation after local extinction

Question 5

demographic connectivity

Answer 5

population growth rates are affected by immigration or emigration

Question 6

genetic connectivity

Answer 6

the degree to which gene flow affects evolution within populations

Question 7

structural connectivity

Answer 7

extent, shape, edges

Question 8

functional connectivity

Answer 8

what organisms can do in a particular landscape
tested with connectivity modelling: species show isolation-by-resistance have reduced mobility and gene flow therefore functional connectivity has been reduced