Social impact of climate change on coastal ecosystem
Answers
The impacts of climate change on
ecosystem structure and function
Nancy B Grimm1*, F Stuart Chapin III2
, Britta Bierwagen3
, Patrick Gonzalez4
, Peter M Groffman5
, Yiqi Luo6
,
Forrest Melton7
, Knute Nadelhoffer8
, Amber Pairis9
, Peter A Raymond10, Josh Schimel11, and
Craig E Williamson12
Recent climate-change research largely confirms the impacts on US ecosystems identified in the 2009 National
Climate Assessment and provides greater mechanistic understanding and geographic specificity for those
impacts. Pervasive climate-change impacts on ecosystems are those that affect productivity of ecosystems or
their ability to process chemical elements. Loss of sea ice, rapid warming, and higher organic inputs affect
marine and lake productivity, while combined impacts of wildfire and insect outbreaks decrease forest pro-
ductivity, mostly in the arid and semi-arid West. Forests in wetter regions are more productive owing to warm-
ing. Shifts in species ranges are so extensive that by 2100 they may alter biome composition across 5–20% of
US land area. Accelerated losses of nutrients from terrestrial ecosystems to receiving waters are caused by both
winter warming and intensification of the hydrologic cycle. Ecosystem feedbacks, especially those associated
with release of carbon dioxide and methane release from wetlands and thawing permafrost soils, magnify the
rate of climate change.
Climate fundamentally controls the distribution of
ecosystems, species ranges, and process rates on
Earth. As a component of the US National Climate
Assessment, to be released in 2014, a group of over 60
ecological experts from academic, governmental, and
nongovernmental organizations assessed the state of
knowledge about how climate change has affected and
will affect species, biodiversity, and ecosystem structure,
function, and services in the US. Here, we summarize key
findings on the impacts of climate change on ecosystems,
focusing on the fluxes of matter and energy and the biotic
and abiotic parts of ecosystems that contribute most to
those fluxes.
Ecosystem patterns and processes, such as rates of pri-
mary productivity or input–output balance of chemical
elements, respond in complex ways to climate change
because of multiple controlling factors. For example,
whether a forest is a carbon (C) source or sink depends
on the balance of primary production and ecosystem
respiration, processes that respond to different drivers.
Physical changes in ecosystems – for instance, changes
in thermal stratification patterns in lakes and oceans,
flood and drying regimes in streams and rivers, or inten-
sification of the hydrologic cycle across large basins –
lead to changes in ecosystem structure and function
that have economic and human consequences. Often
the extremes or changes in timing have greater impact
than changes in average conditions and incur greater
societal impacts and costs. Recognizing these issues, cli-
mate-change action plans and management strategies
have begun to account for forecasted changes in
extremes or seasonality.
n Seven key impacts
Although climate change is affecting US ecosystems in
numerous ways, seven findings emerged from our assess-
ment as representing the most critical climate-change
impacts on ecosystem structure and function in the US,
supported by compelling evidence from the past 4 years
(Figure 1). Only a few of the important references can be
cited in this article due to space limitations, and we referreaders to the WebReferences for additional supporting
references.
Climate effects on sea ice, lakes, and coastal
ecosystems
The late summer extent of Arctic sea ice continues to
decline, with a record low set in 2012 (www.climate-
watch.noaa.gov/article/2012/arctic-sea-ice-breaks-2007-
record-low). This low extent exceeds the previous record
set in 2007 (Figure 2a). The Arctic Ocean is projected to
be ice-free in late summer before the middle of the 21st
century, radically changing patterns of marine productiv-
ity associated with ice edges (Arrigo et al. 2012). In the
Southern Hemisphere, the population size of krill – a key
component of whale and other marine vertebrate diets – is
positively correlated with the extent of sea ice (Atkinson
et al. 2004). As the oceans warm and land-based ice melts,
sea level is rising steadily (Figure 2b) and threatening
habitat-forming species such as corals and mangroves in
coastal ecosystems, as well as infrastructure and liveli-
hoods of people living on coasts (Doney et al. 2012).
Ecosystem state change
Many of the aforementioned
biome shifts are stabilized by
feedbacks that maintain these
ecosystems in their new state,
making it difficult to reverse the
changes. For instance, the Sahel
changed from a tropical forest to
grassland and then to desert
within a few thousand years
(Kröpelin et al. 2008). Rapid or
abrupt transitions, such as deser-
tification or collapse of coral
reefs, may occur when a thresh-
old is crossed (Scheffer et al.
2001).
Answer:
Recent literature illustrates the economic and social challenges facing cities around the world as a result of climate change including energy shortages, damaged infrastructure, increasing losses to industry, heat-related mortality and illness, and scarcity of food and water. These challenges are interrelated.