Soil animals are getting smaller with climate change

Date:
July 28, 2020
Source:
Helmholtz Centre for Environmental Research - UFZ
Summary:
The biomass of small animals that decompose plants in the soil
and thus maintain its fertility is declining both as a result of
climate change and over-intensive cultivation. To their surprise,
however, scientists have discovered that this effect occurs in two
different ways: while the changing climate reduces the body size
of the organisms, cultivation reduces their frequency. Even by
farming organically, it is not possible to counteract all negative
consequences of climate change.



FULL STORY ==========================================================================
The biomass of small animals that decompose plants in the soil and thus maintain its fertility is declining both as a result of climate change
and over-intensive cultivation. To their surprise, however, scientists
have discovered that this effect occurs in two different ways: while
the changing climate reduces the body size of the organisms, cultivation reduces their frequency. Even by farming organically, it is not possible
to counteract all negative consequences of climate change.


========================================================================== Today, life in the soil must contend with several problems at once. The
biomass of small animals that decompose plants in the soil and thus
maintain its fertility is declining both as a result of climate change
and over-intensive cultivation. To their surprise, however, scientists
from the Helmholtz Centre for Environmental Research (UFZ) and the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig
have discovered that this effect occurs in two different ways: while
the changing climate reduces the body size of the organisms, cultivation reduces their frequency. Even by farming organically, it is not possible
to counteract all negative consequences of climate change, the researchers
warn in the trade journal eLife.

Largely unnoticed and in secret, an army of tiny service providers works
below our feet. Countless small insects, arachnids and other soil dwellers
are indefatigably busy decomposing dead plants and other organic material,
and recycling the nutrients they contain. However, experts have long
feared that these organisms, which are so important for soil fertility
and the functioning of ecosystems, are increasingly coming under stress.

On the one hand, they are confronted with the consequences of climate
change, which challenges them with high temperatures and unusual
precipitation conditions with more frequent droughts. On the other
hand, they also suffer from over-intensive land use. If, for example,
a meadow is turned into a field, soil animals find fewer niches and food sources there. Intensive ploughing, mowing or grazing, as well as the
use of pesticides and large amounts of fertilizer also have a negative
effect. But what happens when soil life is faced with both challenges at
the same time? "Until now, we knew almost nothing about this," says Dr
Martin Scha"dler from the UFZ. But he and his colleagues at the UFZ and
iDiv have very good opportunities to pursue such complex questions. The ecologist coordinates the "Global Change Experimental Facility" (GCEF) in
Bad Lauchsta"dt near Halle. There, researchers can simulate the climate
of the future on arable and grassland plots used with varying degrees
of intensity. In large steel constructions reminiscent of greenhouses
without a roof or walls, they recreate a scenario that could be typical
for the region between 2070 and 2100: it is about 0.6 degrees warmer than today, in spring and autumn there is ten percent more precipitation and
summers are about 20 percent drier. A team led by Martin Scha"dler and
doctoral student Rui Yin has now investigated how these conditions affect
mites and springtails. Both groups have many decomposers in their ranks,
which play an important role in the nutrient cycles in the soil.

The results show that these soil animals are likely to dwindle even
further due to climate change. "It is likely that not only smaller species
will prevail, but also smaller individuals within the same species,"
says Martin Scha"dler.

In any case, the examined specimens on the areas with higher temperatures
and changed precipitation were on average about ten percent smaller than
on the comparable areas with today's climate. Biologists have so far been familiar with such connections between body size and climate primarily in larger animals. For example, bear species in warm regions of the Earth are significantly smaller than the polar bear found in the Arctic. This is due
to the fact that a small body has a comparatively large surface area over
which it can release heat -- which is an advantage in the tropics, but
easily leads to cooling in polar regions. In poikilothermal animals such
as insects, high temperatures also stimulate metabolism and developmental speed. "This creates new generations faster, but they remain smaller,"
explains Martin Scha"dler. If the mites and springtails from the plots
with an altered climate are weighed, the total weight is therefore lower
in comparison with those from the unaffected areas. But this is not good
news. After all, these animals' decomposition performance also depends
on this biomass. Less total weight therefore also means that nutrient
recycling is slowed down. According to the experiment, over-intensive
land use can also trigger a very similar effect.

This is because the biomass in the soil also decreases as a result.

"Interestingly, however, there is another process behind this,"
says Martin Scha"dler, summarising the most important result of the
study. "Unlike the climate, use does not reduce the size of the animals,
but their density." For example, around 47 percent fewer mites and
springtails lived on GCEF plots cultivated conventionally compared with
plots extensively used as meadows.

"The fascinating and sobering thing about it is that the effects of
climate and use hardly influence each other," says the ecologist. Until
now, many experts had hoped that eco-friendly agriculture could offer
some kind of insurance against the negative consequences of climate
change. After all, organic farming generally leads to a more diverse
community in fields and grassland. However, it is thought that this
makes such ecosystems less susceptible to climatic disturbances than conventionally used areas.

Yet when it comes to maintaining the performance of soil animals, this
strategy does not seem to work: changes in temperature and precipitation
reduce their biomass regardless of cultivation. "So not everything
that threatens to break down as a result of warming can be saved by environmentally friendly land use," says Martin Scha"dler in summary. In
order to mitigate the consequences of climate change, it is therefore
necessary to tackle greenhouse gases directly - - and as quickly as
possible. "We can't assume that we'll come up with anything else."

========================================================================== Story Source: Materials provided by Helmholtz_Centre_for_Environmental_Research_-_UFZ. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Rui Yin, Julia Siebert, Nico Eisenhauer, Martin Scha"dler. Climate
change
and intensive land use reduce soil animal biomass via dissimilar
pathways. eLife, 2020; 9 DOI: 10.7554/eLife.54749 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200728113520.htm

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